php{} block-level scope detailed

This article is mainly to share with you {} block-level scopes and and && or | | Priority issues, hope to help everyone.

and && or | | Priority issues:

Priority of and or is lower than && | | , and below =.
So $b1 = $bA and $bB the first operation is $b1 = $bA .

$bA = true; $bB = false; $b 1 = $bA and $bB; $b 2 = $bA && $bB; Var_dump ($b 1); $b 1 = truevar_dump ($b 2); $b 2 = False$ba = false; $bB = true; $b 3 = $bA or $bB; $b 4 = $bA | | $bB; Var_dump ($b 3); $b 3 = falsevar_dump ($b 4); $b 4 = True

{} block-level scope:

Outside of {} in PHP, it is possible to fetch its internal values. PHP has a function scope, but no block-level scope.

if (1) {    $a = 123;} Print_r ($a);  $a = 123;

for ($i = 0; $i < $i + +) {for    ($j = 0; $j <; $j + +) {        $k = 777;    }} Var_dump ($j);//Output 10var_dump ($K);//Output 777

$arr = [1, 2, 4];foreach ($arr as & $val) {    $val  *= 2;} $val = [];//re-assigned $val[0]=9; $val [1]=10;var_dump ($arr, $val); output: Array (3) {  [0]=>  int (2)  [1]=>  Int (4)  [2]=>  &array (2) {    [0]=>    int (9)    [1]=>    int.  }}array (2) {  [0]=>  Int (9)  [1]=>  int (10)}

Because $arr as &$val , looping to a third element,

Val Although the re-assignment is an empty array, subsequent modifications will still affect the

Val is a reference, and subsequent modifications will affect it unless unset ($val) is added.