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Comparison operators == (equality operator) and === (identity operator) are used for comparison two values. They are also known as the Loose equals (==) and Strict equals (===) operators.
Symbol | Name | Example | Output result |
---|---|---|---|
== | Equals | $a == $b | Ignore the type, TRUE if $a is equal to $b |
=== | Constantly equal to | $a === $b | TRUE if $a is equal to $b and the type is the same |
PHP Operators There are many operators in PHP, but the == and === operators perform similar tasks strictly or arbitrarily.
Equality operation == will temporarily convert the data type when comparing two values, while === (identical operator) does not need to perform any type conversion, so the calculation amount is reduced and the speed is faster .
Case 1:
<?php // 0 == 0 -> 类型相同返回 true // 转换完成,然后 // 检查是否相等 var_dump(0 == "a"); // 1 == 1 -> true var_dump("1" == "01"); // 10 == 10 -> true var_dump("10" == "1e1"); // 100 == 100 -> true var_dump(100 == "1e2"); // 0 === "a" -> 这种情况为 false // 转换不仅完成 // 还检查是否存在 // 是否相等 var_dump(0 === "a"); // "1" === "01" -> false var_dump("1" === "01"); // "10" === "1e1" -> false var_dump("10" === "1e1"); // 100 == "1e2" -> false var_dump(100 === "1e2"); switch ("a") { case 0: echo "In first case"; break; // 永远不会匹配 "a" 选项 // 因为 switch 使用的是 == case "a": echo "In sceond case"; break; } ?>
Output:
bool(true)
bool(true)
bool(true)
bool(true)
bool(false)
bool(false)
bool(false)
bool(false)
In first case
Case 2:
<?php // TRUE - 以下表达式等同于 (bool)1 == TRUE var_dump(1 == TRUE); // TRUE - 以下表达式等同于 (bool)0 == FALSE var_dump(0 == FALSE); // FALSE - 1 不全等于 TRUE // 1 是整形, TRUE 是布尔型 var_dump(1 === TRUE); // FALSE - 0 不全等于 FALSE // 0 是整形, FALSE 是布尔型 var_dump(0 === FALSE); ?>
Output:
bool(true)
bool(true)
bool(false)
bool(false)
Note: === operator 'type comparison is relatively safe', will only return TRUE when two values have the same type and value, use == will return TRUE if the values are equal.
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