OPcache configuration options

Runtime Runtime

Constants

Title

opcache.enablebool

Enables the opcode cache. When disabled, code is not optimised or cached. The setting opcache.enable can not be enabled at runtime through ini_set(), it can only be disabled. Trying to enable it in a script will generate a warning.

opcache.enable_clibool

Enables the opcode cache for the CLI version of PHP.

opcache.memory_consumptionint

The size of the shared memory storage used by OPcache, in megabytes. The minimum permissible value is "8", which is enforced if a smaller value is set.

When the JIT is enabled, the shared memory segment also holds the JIT buffer, so its total size is this value plus opcache.jit_buffer_size. OPcache first attempts to allocate the segment using HUGE PAGES, and silently falls back to regular pages when the operating system has not set aside enough of them.

opcache.interned_strings_bufferint

The amount of memory used to store interned strings, in megabytes. The maximum value is 32767 on 64bit architectures, and 4095 on 32bit architectures.

Note

Prior to PHP 8.4.0, the maximum value was 4095 megabytes on all architectures.

opcache.max_accelerated_filesint

The maximum number of keys (and therefore scripts) in the OPcache hash table. The actual value used will be the first number in the set of prime numbers { 223, 463, 983, 1979, 3907, 7963, 16229, 32531, 65407, 130987, 262237, 524521, 1048793 } that is greater than or equal to the configured value. The minimum value is 200. The maximum value is 1000000. Values outside of this range are clamped to the permissible range.

opcache.max_wasted_percentageint

The maximum percentage of wasted memory that is allowed before a restart is scheduled, if there is insufficient free memory. The maximum permissible value is "50", which is enforced if a larger value is set.

opcache.use_cwdbool

If enabled, OPcache appends the current working directory to the script key, thereby eliminating possible collisions between files with the same base name. Disabling this directive improves performance, but may break existing applications.

opcache.validate_timestampsbool

If enabled, OPcache will check for updated scripts every opcache.revalidate_freq seconds. When this directive is disabled, you must reset OPcache manually via opcache_reset(), opcache_invalidate() or by restarting the Web server for changes to the filesystem to take effect.

Note

OPcache may still validate the timestamp of a file at compile-time if opcache.file_update_protection or opcache.max_file_size options are set to non-zero values.

opcache.revalidate_freqint

How often to check script timestamps for updates, in seconds. 0 will result in OPcache checking for updates on every request.

This configuration directive is ignored if opcache.validate_timestamps is disabled.

opcache.revalidate_pathbool

If disabled, existing cached files using the same include_path will be reused. Thus, if a file with the same name is elsewhere in the include_path, it won't be found.

opcache.save_commentsbool

If disabled, all documentation comments will be discarded from the opcode cache to reduce the size of the optimised code. Disabling this configuration directive may break applications and frameworks that rely on comment parsing for annotations, including Doctrine, Zend Framework 2 and PHPUnit.

opcache.fast_shutdownbool

If enabled, a fast shutdown sequence is used that doesn't free each allocated block, but relies on the Zend Engine memory manager to deallocate the entire set of request variables en masse.

This directive has been removed in PHP 7.2.0. A variant of the fast shutdown sequence has been integrated into PHP and will be automatically used if possible.

opcache.enable_file_overridebool

When enabled, the opcode cache will be checked for whether a file has already been cached when file_exists(), is_file() and is_readable() are called. This may increase performance in applications that check the existence and readability of PHP scripts, but risks returning stale data if opcache.validate_timestamps is disabled.

opcache.optimization_levelint

A bitmask that controls which optimisation passes are executed. The default value is 0x7FFEBFFF, which enables all safe optimizations. Disabling optimizations or enabling unsafe optimizations is mostly useful for debugging/developing the optimizer.

Each bit in the bitmask enables a specific optimization pass:

Bit	Pass Name	Description	Default
0	PASS_1	Simple peephole optimizations	On
1	PASS_2	Unused (got merged into PASS_1)	On
2	PASS_3	Simple jump optimization	On
3	PASS_4	Call optimization	On
4	PASS_5	Control Flow Graph based optimization	On
5	PASS_6	Data Flow Analysis based optimization	On
6	PASS_7	Whether call graph should be used for SSA-based optimizations	On
7	PASS_8	Sparse conditional constant propagation	On
8	PASS_9	Temporary variable optimization	On
9	PASS_10	Removal of NOP opcodes	On
10	PASS_11	Literal compaction	On
11	PASS_12	Pre-compute call stack size	On
12	PASS_13	Unused variable removal	On
13	PASS_14	Dead code elimination	On
14	PASS_15	Collect and substitute constant declarations (unsafe)	Off
15	PASS_16	Trivial function inlining (part of call optimization)	On
16	(Flag)	Ignore possibility of operator overloading (unsafe)	Off

Note

Safe optimizations (enabled by default) preserve the exact behavior of PHP code while improving performance. They include dead code elimination, constant folding, and jump optimization.

Unsafe optimizations (disabled by default) may alter behavior in edge cases:

• Bit 14: Collecting constants. Constants are substituted at compile-time, ignoring runtime declaration order:

  phpCopy

  <?php
  echo getA();         // Outputs: "hello" instead of throwing an Error
  const A = "hello";
  function getA() { return A; }

• Bit 16: Ignoring operator overloading. Unsafe when using classes with do_operation (e.g. GMP, BCMath) in arithmetic operations. With type declarations, the optimizer can apply the same optimizations safely.

opcache.inherited_hackbool

This configuration directive is ignored.

opcache.dups_fixbool

This hack should only be enabled to work around "Cannot redeclare class" errors.

opcache.blacklist_filenamestring

The location of the OPcache blacklist file. A blacklist file is a text file containing the names of files that should not be accelerated, one per line. Wildcards are allowed, and prefixes can also be provided. Lines starting with a semi-colon are ignored as comments.

A simple blacklist file might look as follows:

phpCopy

; Matches a specific file.
/var/www/broken.php
; A prefix that matches all files starting with x.
/var/www/x
; A wildcard match.
/var/www/*-broken.php

opcache.max_file_sizeint

The maximum file size that will be cached, in bytes. If this is 0, all files will be cached.

opcache.consistency_checksint

If non-zero, OPcache will verify the cache checksum every N requests, where N is the value of this configuration directive. This should only be enabled when debugging, as it will impair performance.

Note

Disabled as of 8.1.18 and 8.2.5. Removed as of PHP 8.3.0.

opcache.force_restart_timeoutint

The length of time to wait for a scheduled restart to begin if the cache isn't active, in seconds. If the timeout is hit, then OPcache assumes that something is wrong and will kill the processes holding locks on the cache to permit a restart.

If opcache.log_verbosity_level is set to 2 or above, a warning will be recorded in the error log when this occurs.

This directive is not supported on Windows.

opcache.error_logstring

The error log for OPcache errors. An empty string is treated the same as stderr, and will result in logs being sent to standard error (which will be the Web server error log in most cases).

opcache.log_verbosity_levelint

The log verbosity level. By default, only fatal errors (level 0) and errors (level 1) are logged. Other levels available are warnings (level 2), information messages (level 3) and debug messages (level 4).

opcache.record_warningsbool

If enabled, OPcache will record compile-time warnings and replay them on the next include, even if it is served from cache.

opcache.preferred_memory_modelstring

The preferred memory model for OPcache to use. If left empty, OPcache will choose the most appropriate model, which is the correct behaviour in virtually all cases.

Possible values include mmap, shm, posix and win32.

opcache.protect_memorybool

Protects shared memory from unexpected writes while executing scripts. This is useful for internal debugging only.

opcache.mmap_basestring

The base used for shared memory segments on Windows. All PHP processes have to map shared memory into the same address space. Using this directive allows "Unable to reattach to base address" errors to be fixed.

opcache.restrict_apistring

Allows calling OPcache API functions only from PHP scripts which path is started from specified string. The default "" means no restriction.

opcache.file_update_protectionstring

Prevents caching files that are less than this number of seconds old. It protects from caching of incompletely updated files. In case all file updates are atomic, performance can be increased by setting this to 0. This will allow files to be cached immediately.

opcache.huge_code_pagesbool

Enables or disables copying of PHP code (text segment) into HUGE PAGES. This should improve performance, but requires appropriate OS configuration. Only the text segment of the PHP binary is remapped; the shared memory segment described under opcache.memory_consumption is unaffected by this directive. When the remapping fails, OPcache emits an E_WARNING. Available on Linux as of PHP 7.0.0, and on FreeBSD as of PHP 7.4.0.

opcache.lockfile_pathstring

Absolute path used to store shared lockfiles (for *nix only)

opcache.opt_debug_levelstring

Produces opcode dumps for debugging different stages of optimizations. 0x10000 will output opcodes as the compiler produced them before any optimization occurs while 0x20000 will output optimized codes.

opcache.file_cachestring

Enables and sets the second level cache directory. It should improve performance when SHM memory is full, at server restart or SHM reset. The default "" disables file based caching.

opcache.file_cache_onlybool

Enables or disables opcode caching in shared memory.

Note

Prior to PHP 8.1.0, disabling this directive with an already populated file cache required to manually clear the file cache.

opcache.file_cache_consistency_checksbool

Enables or disables checksum validation when script loaded from file cache.

opcache.file_cache_fallbackbool

Implies opcache.file_cache_only=1 for a certain process that failed to reattach to shared memory (Windows only). Explicitly enabling the file cache is required.

Caution

Disabling this configuration option may prevent processes to start, and is therefore discouraged.

opcache.validate_permissionbool

Validates the cached file permissions against the current user.

opcache.validate_rootbool

Prevents name collisions in chroot'ed environments. This should be enabled in all chroot'ed environments to prevent access to files outside the chroot.

opcache.preloadstring

Specifies a PHP script that is going to be compiled and executed at server start-up, and which may preload other files, either by include()ing them or by using the opcache_compile_file() function. All the entities (e.g. functions and classes) defined in these files will be available to requests out of the box, until the server is shut down.

Note

Preloading is not supported on Windows.

opcache.preload_userstring

Lets the preloading to be run as the specified system user. This is useful for servers that startup as root before switching to an unprivileged system user. Preloading as root is not allowed by default for security reasons, unless this directive is explicitly set to root. As of PHP 8.3.0, this directive does not need to be set in order to allow preloading while running as root when using the Sapi or phpdbg SAPI.

opcache.cache_idstring

On Windows, all processes running the same PHP SAPI under the same user account having the same cache ID share a single OPcache instance. The value of the cache ID can be freely chosen.

Tip

For IIS, different application pools can have their own OPcache instance by using the environment variable APP_POOL_ID as opcache.cache_id.

opcache.jitstring|int

For typical usage, this option accepts one of four string values:

• disable: Completely disabled, cannot be enabled at runtime.
• off: Disabled, but can be enabled at runtime.
• tracing/on: Use tracing JIT. Recommended for most users. Prior to PHP 8.4.0, this was the default value; as of PHP 8.4.0 the default is disable.
• function: Use function JIT.

For advanced usage, this option accepts a 4-digit integer CRTO, where the digits mean:

C (CPU-specific optimization flags)

• 0: Disable CPU-specific optimization.
• 1: Enable use of AVX, if the CPU supports it.

R (register allocation)

• 0: Don't perform register allocation.
• 1: Perform block-local register allocation.
• 2: Perform global register allocation.

T (trigger)

• 0: Compile all functions on script load.
• 1: Compile functions on first execution.
• 2: Profile functions on first request and compile the hottest functions afterwards.
• 3: Profile on the fly and compile hot functions.
• 4: Currently unused.
• 5: Use tracing JIT. Profile on the fly and compile traces for hot code segments.

O (optimization level)

• 0: No JIT.
• 1: Minimal JIT (call standard VM handlers).
• 2: Inline VM handlers.
• 3: Use type inference.
• 4: Use call graph.
• 5: Optimize whole script.

The "tracing" mode corresponds to CRTO = 1254, the "function" mode corresponds to CRTO = 1205.

Note

As of PHP 8.4.0, if JIT is enabled, PHP exits with a fatal error during startup when JIT initialization fails.

opcache.jit_buffer_sizeint

The amount of shared memory to reserve for compiled JIT code. A zero value disables the JIT.

Shorthandbytes

opcache.jit_debugint

A bit mask specifying which JIT debug output to enable. For possible values, please consult zend_jit.h (search for macro definitions beginning with ZEND_JIT_DEBUG).

opcache.jit_bisect_limitint

Debugging option that disables JIT compilation after compiling a certain number of functions. This may be helpful to bisect the source of a JIT miscompilation. Note: this option only works when JIT trigger is set to 0 (compile on script load) or 1 (compile on first execution), e.g. opcache.jit=1215. See more in opcache.jit option.

opcache.jit_prof_thresholdfloat

When using the "profile on first request" trigger mode, this threshold determines whether a function is considered hot. The number of calls to the function divided by the number of calls to all functions must be above the threshold. For example, a threshold of 0.005 means that functions that made up more than 0.5% of all calls will be JIT compiled.

opcache.jit_max_root_tracesint

Maximum number of root traces. The root trace is an execution flow taking one path through the code firstly, which is a unit of JIT compilation. JIT will not compile new code if it reaches this limit.

opcache.jit_max_side_tracesint

Maximum number of side traces a root trace may have. The side trace is another execution flow that does not follow the path of compiled root trace. Side traces belonging to the same root trace will not be compiled if it reaches this limit.

opcache.jit_max_exit_countersint

Maximum number of side trace exit counters. This limits the total number of side traces there may be, across all root traces.

opcache.jit_hot_loopint

After how many iterations a loop is considered hot. Valid value range is [0,255]; for any setting out of this range, e.g. -1 or 256, default value will be used instead. 0 will disable JIT to trace and compile any loops.

Note

It is recommended that this parameter is set to a prime number, to prevent it from being a multiple of loop iteration counts.

opcache.jit_hot_funcint

After how many calls a function is considered hot. Valid value range is [0,255]; for any setting out of this range, e.g. -1 or 256, default value will be used instead. 0 will disable JIT to trace and compile any functions.

opcache.jit_hot_returnint

After how many returns a return is considered hot. Valid value range is [0,255]; for any setting out of this range, e.g. -1 or 256, default value will be used instead. 0 will disable JIT to trace and compile any returns.

opcache.jit_hot_side_exitint

After how many exits a side exit is considered hot. Valid value range is [0,255]; for any setting out of this range, e.g. -1 or 256, default value will be used instead. 0 will disable JIT to trace and compile any side exits.

opcache.jit_blacklist_root_traceint

Maximum number of times the compilation of a root trace is attempted before it is blacklisted.

opcache.jit_blacklist_side_traceint

Maximum number of times the compilation of a side trace is attempted before it is blacklisted.

opcache.jit_max_loop_unrollsint

Maximum number of attempts to unroll a loop in a side trace, trying to reach the root trace and close the outer loop.

opcache.jit_max_recursive_callsint

Maximum number of unrolled recursive call loops.

opcache.jit_max_recursive_returnsint

Maximum number of unrolled recursive return loops.

opcache.jit_max_polymorphic_callsint

Maximum number of attempts to inline polymorphic (dynamic or method) calls. Calls above this limit are treated as megamorphic and are not inlined.