Inequality by Value and Type in PHP

In addition to the operator !=, there is also the operator !==, which takes type into account during comparison. Let's look at the differences between them with examples.

Suppose two numbers 3 are compared using the operator !=. This operator compares values for being NOT equal. Since our values are indeed equal, '-' will be displayed:

php<?php
  if (3 != 3) {
    echo '+++';
  } else {
    echo '---'; // this will execute because the values are equal
  }
?>

Now suppose one of our values is in quotes. In this case, the operator != will still consider them equal (since the value matches, and the type is not important for this operator) and will again output '-':

php<?php
  if ('3' != 3) {
    echo '+++';
  } else {
    echo '---'; // this will execute because the values are equal
  }
?>

Let's now compare two numbers 3 using the operator !==. It will also consider them equal and output '-':

php<?php
  if (3 !== 3) {
    echo '+++';
  } else {
    echo '---'; // this will execute because the values are equal
  }
?>

But if we now put one of the threes in quotes, the operator !== will consider our threes unequal, because, although their values match, they have different types:

php<?php
  if ('3' !== 3) {
    echo '+++'; // this will execute because the values are NOT equal
  } else {
    echo '---';
  }
?>

php<?php
  $test1 = '3';
  $test2 = '3';
    
  if ($test1 != $test2) {
    echo '+++';
  } else {
    echo '---';
  }
?>

php<?php
  $test1 = '3';
  $test2 = '3';
    
  if ($test1 !== $test2) {
    echo '+++';
  } else {
    echo '---';
  }
?>

php<?php
  $test1 = 3;
  $test2 = '3';
    
  if ($test1 != $test2) {
    echo '+++';
  } else {
    echo '---';
  }
?>

php<?php
  $test1 = 3;
  $test2 = '3';
    
  if ($test1 !== $test2) {
    echo '+++';
  } else {
    echo '---';
  }
?>

php<?php
  $test1 = 3;
  $test2 = 2;
    
  if ($test1 !== $test2) {
    echo '+++';
  } else {
    echo '---';
  }
?>