Operators

Arithmetic operators

operator	description	example	result
`+`	addition	`$x + $y`	sum of `$x` and `$y`
`-`	subtraction	`$x - $y`	difference of `$x` and `$y`
`*`	multiplication	`$x * $y`	product of `$x` and `$y`
`/`	division	`$x / $y`	quotient of `$x` and `$y`
`%`	modulus	`$x % $y`	remainder of `$x` divided by `$y`
`**`	power	`$x ** $y`	`$x` to the power `$y`

Open course/arithmetic_operators.php

php

<article>
    <?php
    $x = 10;
    $y = 3;
    echo "<p> \$x = $x </p>\n";
    echo "<p> \$y = $y </p>\n";
    echo "<hr>\n";
    echo "<pre><code> \$x + \$y = $x + $y = " . ($x + $y) . "</code></pre>\n";
    echo "<pre><code> \$x - \$y = $x - $y = " . ($x - $y) . "</code></pre>\n";
    echo "<pre><code> \$x * \$y = $x * $y = " . ($x * $y) . "</code></pre>\n";
    echo "<pre><code> \$x / \$y = $x / $y = " . ($x / $y) . "</code></pre>\n";
    echo "<pre><code> \$x % \$y = $x % $y = " . ($x % $y) . "</code></pre>\n";
    echo "<pre><code> \$x ** \$y = $x ** $y = " . ($x ** $y) . "</code></pre>\n";
    ?>
</article>

<article>
    <?php
    $x = 10;
    $y = 3;
    echo "<p> \$x = $x </p>\n";
    echo "<p> \$y = $y </p>\n";
    echo "<hr>\n";
    echo "<pre><code> \$x + \$y = $x + $y = " . ($x + $y) . "</code></pre>\n";
    echo "<pre><code> \$x - \$y = $x - $y = " . ($x - $y) . "</code></pre>\n";
    echo "<pre><code> \$x * \$y = $x * $y = " . ($x * $y) . "</code></pre>\n";
    echo "<pre><code> \$x / \$y = $x / $y = " . ($x / $y) . "</code></pre>\n";
    echo "<pre><code> \$x % \$y = $x % $y = " . ($x % $y) . "</code></pre>\n";
    echo "<pre><code> \$x ** \$y = $x ** $y = " . ($x ** $y) . "</code></pre>\n";
    ?>
</article>

REMARKS

If you escape the dollar sign in a double-quoted (or heredoc) string, the corresponding variable won't be interpolated: echo "<p> \$x = $x </p>\n"; results in $x = 10 as output
You can't (easily) include arithmetic operations in a double quoted string. Therefore, we resort to string concatenation in the statement echo "<pre><code> \$x + \$y = $x + $y = " . ($x + $y) . "</code></pre>\n";.
You should also enclose the calculation ($x + $y) with round brackets to get an error-free statement.
- As an alternative, you could use an additional variable $sum = $x + $y, after which you can write
  echo "<pre><code> \$x + \$y = $x + $y = $sum</code></pre>\n";

Assignment operators

operator	description	example	result
`=`	assign	`$x = $y`
`+=`	add and assign	`$x += $y`	`$x = $x + $y`
`-=`	subtract and assign	`$x -= $y`	`$x = $x - $y`
`*=`	multiply and assign	`$x *= $y`	`$x = $x * $y`
`/=`	divide and assign quotient	`$x /= $y`	`$x = $x / $y`
`%=`	divide and assign modulus	`$x %= $y`	`$x = $x % $y`
`.=`	concatenate and assign	`$x .= $y`	`$x = $x . $y`
`++`	increment and assign	`$x++`	`$x = $x + 1`
`--`	decrement and assign	`$x--`	`$x = $x - 1`

Open course/assignment_operators.php

php

<article>
    <?php
    $x = 10;
    $y = 2;
    $z = 3;
    echo "<p> \$x = $x </p>\n";
    echo "<p> \$y = $y </p>\n";
    echo "<p> \$z = $z </p>\n";
    echo "<hr>\n";

    echo "<pre><code> \$x += \$y;       // \$x = \$x + \$y = $x + $y </code></pre>\n";
    $x += $y;
    echo "<p> Result: <b>\$x = $x</b></p>\n<hr>\n";

    echo "<pre><code> \$x -= \$z;       // \$x = \$x - \$z = $x - $z </code></pre>\n";
    $x -= $z;
    echo "<p> Result: <b>\$x = $x </b></p>\n<hr>\n";

    echo "<pre><code> \$x *= \$z;       // \$x = \$x * \$z = $x * $z </code></pre>\n";
    $x *= $z;
    echo "<p> Result: <b>\$x = $x </b></p>\n<hr>\n";

    echo "<pre><code> \$x /= \$z;       // \$x = \$x / \$z = $x / $z </code></pre>\n";
    $x /= $z;
    echo "<p> Result: <b>\$x = $x </b></p>\n<hr>\n";

    echo "<pre><code> \$x %= \$y;       // \$x = \$x % \$y = $x % $y </code></pre>\n";
    $x %= $y;
    echo "<p> Result: <b>\$x = $x</b></p>\n<hr>\n";

    echo "<pre><code> \$y++;            // \$y = \$y + 1 = $y + 1 </code></pre>\n";
    $y++;
    echo "<p> Result: <b>\$y = $y </b></p>\n<hr>\n";

    echo "<pre><code> \$z--;            // \$z--; </code></pre>\n";
    $z--;
    echo "<p> Result: <b>\$z = $z </b></p>\n";
    ?>
</article>

<article>
    <?php
    $name = 'John';
    $surname = 'Doe';
    echo "<p> \$name = '$name' </p>\n";
    echo "<p> \$surname = '$surname' </p>\n";
    echo "<hr>\n";

    echo "<pre><code> \$name .= \$surname;    // \$name = \$name . \$surname = '$name' . '$surname' </code></pre>\n";
    $name .= $surname;
    echo "<p> Result: <b>\$name = '$name' </b></p>\n";
    ?>
</article>

<article>
    <?php
    $x = 10;
    $y = 2;
    $z = 3;
    echo "<p> \$x = $x </p>\n";
    echo "<p> \$y = $y </p>\n";
    echo "<p> \$z = $z </p>\n";
    echo "<hr>\n";

    echo "<pre><code> \$x += \$y;       // \$x = \$x + \$y = $x + $y </code></pre>\n";
    $x += $y;
    echo "<p> Result: <b>\$x = $x</b></p>\n<hr>\n";

    echo "<pre><code> \$x -= \$z;       // \$x = \$x - \$z = $x - $z </code></pre>\n";
    $x -= $z;
    echo "<p> Result: <b>\$x = $x </b></p>\n<hr>\n";

    echo "<pre><code> \$x *= \$z;       // \$x = \$x * \$z = $x * $z </code></pre>\n";
    $x *= $z;
    echo "<p> Result: <b>\$x = $x </b></p>\n<hr>\n";

    echo "<pre><code> \$x /= \$z;       // \$x = \$x / \$z = $x / $z </code></pre>\n";
    $x /= $z;
    echo "<p> Result: <b>\$x = $x </b></p>\n<hr>\n";

    echo "<pre><code> \$x %= \$y;       // \$x = \$x % \$y = $x % $y </code></pre>\n";
    $x %= $y;
    echo "<p> Result: <b>\$x = $x</b></p>\n<hr>\n";

    echo "<pre><code> \$y++;            // \$y = \$y + 1 = $y + 1 </code></pre>\n";
    $y++;
    echo "<p> Result: <b>\$y = $y </b></p>\n<hr>\n";

    echo "<pre><code> \$z--;            // \$z--; </code></pre>\n";
    $z--;
    echo "<p> Result: <b>\$z = $z </b></p>\n";
    ?>
</article>

<article>
    <?php
    $name = 'John';
    $surname = 'Doe';
    echo "<p> \$name = '$name' </p>\n";
    echo "<p> \$surname = '$surname' </p>\n";
    echo "<hr>\n";

    echo "<pre><code> \$name .= \$surname;    // \$name = \$name . \$surname = '$name' . '$surname' </code></pre>\n";
    $name .= $surname;
    echo "<p> Result: <b>\$name = '$name' </b></p>\n";
    ?>
</article>

Comparison operators

operator	description	example	result
`==`	equal	`$x == $y`	`true` if `$x` is equal to `$y`
`===`	identical	`$x === $y`	`true` if `$x` is equal to `$y` and they are of the same type
`!=` `<>`	not equal	`$x != $y` `$x <> $y`	`true` if `$x` is not equal to `$y`
`!==`	not identical	`$x !== $y`	`true` if `$x` is not equal to `$y` or they are not of the same type
`<`	less than	`$x < $y`	`true` if `$x` is less than `$y`
`<=`	less than or equal to	`$x <= $y`	`true` if `$x` is less than or equal to `$y`
`>`	greater than	`$x > $y`	`true` if `$x` is greater than `$y`
`>=`	greater than or equal to	`$x >= $y`	`true` if `$x` is greater than or equal to `$y`

Open course/comparison_operators.php

php

<article>
    <?php
    $x1 = 10;
    $x2 = '10';
    $y = 5;
    echo "<p> \$x1 = $x1 </p>\n";
    echo "<p> \$x2 = '$x2' </p>\n";
    echo "<p> \$y = $y </p>\n";
    echo "<hr>\n";
    echo "<pre><code> (\$x1 == \$x2) = ($x1 == '$x2') = " . ($x1 == $x2) . "</code></pre>\n";
    echo "<pre><code> (\$x1 === \$x2) = ($x1 === '$x2') = " . ($x1 === $x2) . "</code></pre>\n";
    echo "<pre><code> (\$x1 != \$y) = ($x1 != $y) = " . ($x1 != $y) . "</code></pre>\n";
    echo "<pre><code> (\$x2 &lt;&gt; \$y) = ('$x2' &lt;&gt; $y) = " . ($x2 <> $y) . "</code></pre>\n";
    echo "<pre><code> (\$x1 &lt; \$y) = ($x1  &lt; $y) = " . ($x1 < $y) . "</code></pre>\n";
    echo "<pre><code> (\$x1 &gt; \$y) = ($x1 &gt; $y) = " . ($x1 > $y) . "</code></pre>\n";
    echo "<pre><code> (\$x2 &gt; \$y) = ('$x2' &gt; $y) = " . ($x2 > $y) . "</code></pre>\n";
    ?>
</article>

<article>
    <?php
    $x1 = 10;
    $x2 = '10';
    $y = 5;
    echo "<p> \$x1 = $x1 </p>\n";
    echo "<p> \$x2 = '$x2' </p>\n";
    echo "<p> \$y = $y </p>\n";
    echo "<hr>\n";
    echo "<pre><code> (\$x1 == \$x2) = ($x1 == '$x2') = " . ($x1 == $x2) . "</code></pre>\n";
    echo "<pre><code> (\$x1 === \$x2) = ($x1 === '$x2') = " . ($x1 === $x2) . "</code></pre>\n";
    echo "<pre><code> (\$x1 != \$y) = ($x1 != $y) = " . ($x1 != $y) . "</code></pre>\n";
    echo "<pre><code> (\$x2 &lt;&gt; \$y) = ('$x2' &lt;&gt; $y) = " . ($x2 <> $y) . "</code></pre>\n";
    echo "<pre><code> (\$x1 &lt; \$y) = ($x1  &lt; $y) = " . ($x1 < $y) . "</code></pre>\n";
    echo "<pre><code> (\$x1 &gt; \$y) = ($x1 &gt; $y) = " . ($x1 > $y) . "</code></pre>\n";
    echo "<pre><code> (\$x2 &gt; \$y) = ('$x2' &gt; $y) = " . ($x2 > $y) . "</code></pre>\n";
    ?>
</article>

REMARK

Notice that true is depicted as 1, while false corresponds to an empty string

Logical operators

operator	example	result
`and` `&&`	`$x and $y` `$x && $y`	`true` if both `$x` and `$y` are true
`or` `		`
`xor`	`$x xor $y`	`true` if either `$x` or `$y` is true, but not both
`!`	`!$x`	`true` if `$x` is `false` (not `true`)

Open course/logical_operators.php

php

<article>
    <?php
    $x = 6;
    $y = 4;
    echo "<p> \$x = $x </p>\n";
    echo "<p> \$y = $y </p>\n";
    echo "<hr>\n";
    echo "<pre><code> (\$x &lt; 8 and \$y &gt; 3) = ($x &lt; 8 and $y &gt; 3) = " . ($x < 8 and $y > 3) . "</code></pre>\n";
    echo "<pre><code> (\$x &lt; 8 && \$y &gt; 6) = ($x &lt; 8 && $y &gt; 6) = " . ($x < 8 && $y > 6) . "</code></pre>\n";
    echo "<pre><code> (\$x &lt; 8 or \$y &gt; 3) = ($x &lt; 8 or $y &gt; 3) = " . ($x < 8 or $y > 3) . "</code></pre>\n";
    echo "<pre><code> (\$x &lt; 8 || \$y &gt; 6) = ($x &lt; 8 || $y &gt; 6) = " . ($x < 8 || $y > 6) . "</code></pre>\n";
    echo "<pre><code> (\$x &lt; 8 xor \$y &gt; 3) = ($x &lt; 8 xor $y &gt; 3) = " . ($x < 8 xor $y > 3) . "</code></pre>\n";
    echo "<pre><code> (\$x &lt; 8 xor \$y &gt; 6) = ($x &lt; 8 xor $y &gt; 6) = " . ($x < 8 xor $y > 6) . "</code></pre>\n";
    echo "<pre><code> !(\$x == \$y) = !($x == $y) = " . !($x == $y) . "</code></pre>\n";
    ?>
</article>

<article>
    <?php
    $x = 6;
    $y = 4;
    echo "<p> \$x = $x </p>\n";
    echo "<p> \$y = $y </p>\n";
    echo "<hr>\n";
    echo "<pre><code> (\$x &lt; 8 and \$y &gt; 3) = ($x &lt; 8 and $y &gt; 3) = " . ($x < 8 and $y > 3) . "</code></pre>\n";
    echo "<pre><code> (\$x &lt; 8 && \$y &gt; 6) = ($x &lt; 8 && $y &gt; 6) = " . ($x < 8 && $y > 6) . "</code></pre>\n";
    echo "<pre><code> (\$x &lt; 8 or \$y &gt; 3) = ($x &lt; 8 or $y &gt; 3) = " . ($x < 8 or $y > 3) . "</code></pre>\n";
    echo "<pre><code> (\$x &lt; 8 || \$y &gt; 6) = ($x &lt; 8 || $y &gt; 6) = " . ($x < 8 || $y > 6) . "</code></pre>\n";
    echo "<pre><code> (\$x &lt; 8 xor \$y &gt; 3) = ($x &lt; 8 xor $y &gt; 3) = " . ($x < 8 xor $y > 3) . "</code></pre>\n";
    echo "<pre><code> (\$x &lt; 8 xor \$y &gt; 6) = ($x &lt; 8 xor $y &gt; 6) = " . ($x < 8 xor $y > 6) . "</code></pre>\n";
    echo "<pre><code> !(\$x == \$y) = !($x == $y) = " . !($x == $y) . "</code></pre>\n";
    ?>
</article>

Operators ​

Arithmetic operators ​

Assignment operators ​

Comparison operators ​

Logical operators ​

Operators

Arithmetic operators

Assignment operators

Comparison operators

Logical operators