PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate N bytes)

Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 20480 bytes) means the script hit PHP's memory_limit. 134217728 bytes is 128 MB, the default; the "tried to allocate" number is only the last small allocation that failed, not the total needed. Either the job loads too much into memory at once (fix it by processing in chunks), or it really needs more and you raise memory_limit in php.ini or with ini_set(). In the error log the line starts with PHP Fatal error:, and the CLI exits with status 255.

Common values in the message

Raise the limit

memory_limit = 512M

<?php
ini_set('memory_limit', '512M');   // for this script only, before the heavy work

php -d memory_limit=512M script.php           # one CLI run
php --ini                                     # which php.ini the CLI loads
php -r 'echo ini_get("memory_limit"), PHP_EOL;'
COMPOSER_MEMORY_LIMIT=-1 composer update      # Composer only

The CLI and the web server (PHP-FPM, Apache mod_php) usually load different php.ini files: change the one used by the process that fails, then restart PHP-FPM or the web server.

Use less memory instead

<?php
// Read a large file line by line instead of file() or file_get_contents()
$fh = fopen('big.csv', 'r');
while (($row = fgetcsv($fh)) !== false) {
    handle($row);
}
fclose($fh);

// Yield rows one at a time with a generator
function rows(PDO $db): Generator {
    $stmt = $db->query('SELECT * FROM events');
    while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
        yield $row;
    }
}