This question already has an answer here:
how to split received values of an array into a new array?
so from this:
[["+","+","+"],["-","+","+"],["*","+","+"],["\/","+","+"],
to this:
["+"],["+"],["+"],["-"],["+"],["+"],["*"],["+"],["+"],
can someone help me?
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Flatten your array by looping through it
$aFlattened = array();
foreach($aOriginalArray AS $aOperators){
$aFlattened = array_merge($aFlattened, $aOperators);
}