internals
A declared property is cheaper than an array key
One hundred thousand four-field records cost 143.54 bytes each as objects and 397.14 as associative arrays. Where the crossover is, and what one undeclared property costs.
memory
7 posts
internals
Two hundred thousand objects, and the collector never ran
Two hundred thousand objects created and dropped, and zero collections. What puts an object in the root buffer, and why the collector's cost is set by what you keep alive.
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.
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.