PHP gc_collect_cycles() Function: Usage and Examples

Use gc_collect_cycles() when you need to runs the cycle collector and returns the number of cycles collected in a PHP application. The examples below show the actual operation and its limitations.

What Is gc_collect_cycles() in PHP?

Runs the cycle collector and returns the number of cycles collected. The exact signature supported by your installation depends on its PHP version and enabled extensions.

Its syntax is:

gc_collect_cycles(): int

Parameters and return value: The parameter types, optional arguments, references, and return type are shown in the signature above. Optional parameters are marked with an ellipsis in this reference signature.

Example 1: Basic Usage

<?php

echo gc_collect_cycles();

Result: Run the example in an environment that supports the function. Any values depending on operating-system state, installed extensions, process configuration, or network access must be checked on the target server.

Example 2: Different Input or Behavior

<?php

gc_enable(); echo gc_collect_cycles();

Result: Run the example in an environment that supports the function. Any values depending on operating-system state, installed extensions, process configuration, or network access must be checked on the target server.

Practical Example: Applying the Function

<?php

class LoopNode { public ?LoopNode $next = null; } $node = new LoopNode(); $node->next = $node; unset($node); echo gc_collect_cycles();

Result: Run the example in an environment that supports the function. Any values depending on operating-system state, installed extensions, process configuration, or network access must be checked on the target server.

Important Behavior and Edge Cases

Only cyclic garbage is targeted; the number collected depends on runtime state.

Comparison With Related Functions

Common Beginner Mistakes

Key Takeaways

• Runs the cycle collector and returns the number of cycles collected.
• Only cyclic garbage is targeted; the number collected depends on runtime state.
• gc_status() reports collector statistics; gc_collect_cycles() triggers a collection pass.

Use gc_collect_cycles() for the specific operation demonstrated above. Check its prerequisites and handle failure conditions before using it with production data.