performance
Three numbers for one process, and memory_limit reads the middle one
memory_get_usage(), memory_get_usage(true) and ps disagree about one process. What each counts, which one memory_limit reads, and why a one-megabyte string costs two.
memory
5 posts
internals
A by-reference foreach leaves a reference in every element
Walking an array with foreach ($rows as &$row) wraps every element in a zend_reference. On a million integers that is 32 MB the loop never gives back.
internals
What a PHP variable actually is
A zval is sixteen bytes, a value union and a type tag. What that tag says decides whether an assignment copies anything, what a reference costs, and which variable pays.
runtime
PHP-FPM process management in production
pm static, dynamic and ondemand, the memory ceiling nothing enforces, and how to size a pool from measurements rather than guesses.
internals
PHP arrays are not arrays
One structure serves as list, dictionary and set. Packed and hashed layouts, what each costs in memory, and when a conversion happens.