PHP Fatal Error: "Allowed Memory Size Exhausted"

The script outgrew PHP's memory_limit. Raise it for a real workload, but treat it as a leak symptom in long scripts or a plugin/WordPress bloat issue — not something to paper over forever.

What you'll see

Root causes

Genuinely heavy operation vs. low default limit

memory_limit defaults to 128M; big CSV imports, bulk media processing, or large report generation legitimately need more. php -r 'echo ini_get("memory_limit");' shows the current value.

A leak or runaway loop

Queries returning unbounded rows into arrays, appending in a loop without unsetting, or a plugin bug. Raising the limit just delays the same crash — profile before you raise.

Fix it

  1. Confirm the current limit
    php -r 'echo ini_get("memory_limit");' ; php -i | grep -i memory_limit   # web SAPI may differ from CLI
  2. Raise the limit where the workload runs
    # php.ini: memory_limit = 512M ; or .htaccess: php_value memory_limit 512M ; or wp-config.php: define('WP_MEMORY_LIMIT', '512M');
  3. CLI one-off: raise per-command
    php -d memory_limit=1G import.php
  4. If it recurs: find the growth, not just the ceiling
    # log memory_get_usage() at loop iterations; check queries fetching entire tables; wp-cli --skip plugins to isolate a plugin

Field note

WP_MEMORY_LIMIT only affects WordPress; the real ceiling is PHP's memory_limit — set both consistently. Recurring exhaustion on normal traffic is a bug (often a plugin), and unlimited limits just move the crash to OOM at the server level.

Common questions

How high can I safely set memory_limit?

512M-1G covers most real workloads. Beyond that, suspect a leak. The limit exists to protect the server from one bad script — removing it entirely is a self-inflicted DoS risk.

Why does the same import fail at different points each run?

Memory consumption depends on the data flowing through — each run allocates differently before hitting the same ceiling. That randomness signature = leak/loop, not a static workload.

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