simplified GC strategy for long-running / high volume

simple_gc_strategy.php

<?php

define('SCRIPT_MEMORY_CONSUMPTION', memory_get_usage(true));

gc_enable();

/**
 * we might call gc_collect_cycles if
 *   memory_get_usage >= original memory * threshold
 */
define('MEMORY_THRESHOLD',2);

/**
 * only if we're over memory threshold
 *   5.05% probability we call GC manually
 */
define('GC_PROBABILITY', 5.05);

function collectGarbage() {
    $fraction = number_format(GC_PROBABILITY/100, 4) * 10000;
    $rand = mt_rand(1, 10000);
    if($rand < $fraction){
        if((SCRIPT_MEMORY_CONSUMPTION * MEMORY_THRESHOLD) <= memory_get_usage(true)){
            gc_collect_cycles();
        }
    }
}