PHP Type Comparison

Although PHP is a weakly typed language, it is still necessary to understand variable types and their meanings, because we often need to compare PHP variables, including loose and strict comparisons.

  • Loose comparison: use two equal signs==When comparing, only the values are compared, not the types.
  • Strict comparison: use three equal signs===When comparing, in addition to comparing values, it also compares types.

For example, "42" is a string while 42 is an integer.FALSEis a boolean value and"FALSE"is a string.

Example

<?php if(42 == "42") { echo '1. Equal values'; } echo PHP_EOL; //Newline character if(42 === "42") { echo '2. Equal types'; } else { echo '3. Types are not equal'; } ?>

The output of the above example is:

1、值相等
3、类型不相等

Comparing 0, false, null in PHP

Test code:

Example

<?php echo '0 == false: '; var_dump(0 == false); echo '0 === false: '; var_dump(0 === false); echo PHP_EOL; echo '0 == null: '; var_dump(0 == null); echo '0 === null: '; var_dump(0 === null); echo PHP_EOL; echo 'false == null: '; var_dump(false == null); echo 'false === null: '; var_dump(false === null); echo PHP_EOL; echo '"0" == false: '; var_dump("0" == false); echo '"0" === false: '; var_dump("0" === false); echo PHP_EOL; echo '"0" == null: '; var_dump("0" == null); echo '"0" === null: '; var_dump("0" === null); echo PHP_EOL; echo '"" == false: '; var_dump("" == false); echo '"" === false: '; var_dump("" === false); echo PHP_EOL; echo '"" == null: '; var_dump("" == null); echo '"" === null: '; var_dump("" === null);

The output of the above example is:

0 == false: bool(true)
0 === false: bool(false)

0 == null: bool(true)
0 === null: bool(false)

false == null: bool(true)
false === null: bool(false)

"0" == false: bool(true)
"0" === false: bool(false)

"0" == null: bool(false)
"0" === null: bool(false)

"" == false: bool(true)
"" === false: bool(false)

"" == null: bool(true)
"" === null: bool(false)

Other Extensions