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This article mainly shares with you {} block-level scope and and && or || priority issues, I hope it can help everyone.
and or has a lower priority than && || and lower than =.
Therefore $b1 = $bA and $bB
The first operation is $b1 = $bA
.
$bA = true;$bB = false;$b1 = $bA and $bB;$b2 = $bA && $bB; var_dump($b1); // $b1 = truevar_dump($b2); // $b2 = false$bA = false;$bB = true;$b3 = $bA or $bB;$b4 = $bA || $bB; var_dump($b3); // $b3 = falsevar_dump($b4); // $b4 = true
In php, the internal value can be obtained outside {}. PHP has function scope, but not block scope.
if(1){ $a = 123; } print_r($a); // $a = 123;
for ($i = 0; $i < 10; $i++) { for ($j = 0; $j < 10; $j++) { $k = 777; } } var_dump($j);//输出10var_dump($k);//输出777
$arr = [1, 2, 4];foreach ($arr as &$val) { $val *= 2; }$val = [];//重新赋值$val[0]=9;$val[1]=10; var_dump($arr,$val); 输出:array(3) { [0]=> int(2) [1]=> int(4) [2]=> &array(2) { [0]=> int(9) [1]=> int(10) } }array(2) { [0]=> int(9) [1]=> int(10) }
Since $arr as &$val
, loop to the third element,
val. Although it is reassigned to an empty array, subsequent modifications will still affect
val is a reference, and subsequent modifications will affect it. , unless unset($val) is added.
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