Some stuff that I think is important in base PHP is the list of array functions. Theres actually so much you can do with arrays and those functions in base PHP where you don't have access to collections etc. And knowing how to use them is very important.
$array = array_merge_recursive(...$array)
My beloved. This is used to get arrays nested within other arrays to all be on the same level.
debug($anyVariableYouMayWantToDebug)
CakePHP only. PHP Equivalent is print_r(). Is useful to debug certain things and to set a breakpoint right at that place.
var_dump($anyVariableYouMayWantToDump)
Native PHP. Basically echoes any variable with all its details to whatever interface you're working on. Great to see what actual data you get from something like an API.
Theres functions in PHP to measure and display your current and your peak memory usage:
$memoryCurrentlyUsed = memory_get_usage(true) // The parameter makes it take the real allocated usage $memoryPeakUsage = memory_get_peak_usage(true) // These will give back an int value of bytes used memory_reset_peak_usage() // Needs to be run to reset the peak usage, if needed