PHP 5 Operators

Simple answer can be given using expression 4 + 5 is equal to 9. Here 4 and 5 are called operands and + is called operator. PHP language supports following type of operators.

Arithmetic Operators

Comparison Operators

Logical (or Relational) Operators

Assignment Operators

Conditional (or ternary) Operators

String operators

Array operators

Operator Precedence

Bitwise Operators

Arithmetic Operators

The division operator ("/") returns a float value unless the two operands are integers (or strings that get converted to integers) and the numbers are evenly divisible, in which case an integer value will be returned.Operands of modulo are converted to integers (by stripping the decimal part) before processing.

Example -

<?php echo (5 % 3)."\n"; // prints 2 echo (5 % -3)."\n"; // prints 2 echo (-5 % 3)."\n"; // prints -2 echo (-5 % -3)."\n"; // prints -2 ?>

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Comparison operators

Comparison operators, as their name implies, allow you to compare two values. You may also be interested in viewing the type comparison tables,f you compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically. These rules also apply to the switch statement. The type conversion does not take place when the comparison is === or !== as this involves comparing the type as well as the value.

Example -

<?php var_dump(0 == "a"); // 0 == 0 -> true var_dump("1" == "01"); // 1 == 1 -> true var_dump("10" == "1e1"); // 10 == 10 -> true var_dump(100 == "1e2"); // 100 == 100 -> true switch ("a") { case 0: echo "0"; break; case "a": // never reached because "a" is already matched with 0 echo "a"; break; } ?>

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Logical (or Relational) Operators

The PHP logical operators are used to combine conditional statements.

Example -

<?php // -------------------- // foo() will never get called as those operators are short-circuit $a = (false && foo()); $b = (true || foo()); $c = (false and foo()); $d = (true or foo()); // -------------------- // "||" has a greater precedence than "or" // The result of the expression (false || true) is assigned to $e // Acts like: ($e = (false || true)) $e = false || true; // The constant false is assigned to $f before the "or" operation occurs // Acts like: (($f = false) or true) $f = false or true; var_dump($e, $f); // -------------------- // "&&" has a greater precedence than "and" // The result of the expression (true && false) is assigned to $g // Acts like: ($g = (true && false)) $g = true && false; // The constant true is assigned to $h before the "and" operation occurs // Acts like: (($h = true) and false) $h = true and false; var_dump($g, $h); ?>

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Assignment Operators

The basic assignment operator is "=". Your first inclination might be to think of this as "equal to". Don't. It really means that the left operand gets set to the value of the expression on the right (that is, "gets set to").

The value of an assignment expression is the value assigned. That is, the value of "$a = 3" is 3. This allows you to do some tricky things:

Example -

<?php $x1=100; $x2=200; $x3=300; $x4=400; $x5=500; $x1+= 100; echo " $x1 <br />"; $x2-= 200; echo " $x2 <br />"; $x3*= 300; echo " $x3 <br />"; $x4/= 400; echo " $x4 <br />"; $x5%= 500; echo " $x5 <br />"; $x=($y=11)+9; echo " Value of x & y is : $x $y <br />"; ?>

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Conditional (or ternary) Operators

There is one more operator called conditional operator. This first evaluates an expression for a true or false value and then execute one of the two given statements depending upon the result of the evaluation.

Example -

<?php $a = 10; $b = 20; /* If condition is true then assign a to result otheriwse b */ $result = ($a > $b ) ? $a :$b; echo "TEST1 : Value of result is $result<br/>"; /* If condition is true then assign a to result otheriwse b */ $result = ($a < $b ) ? $a :$b; echo "TEST2 : Value of result is $result<br/>"; ?>

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String operators

There are two string operators. The first is the concatenation operator ('.'), which returns the concatenation of its right and left arguments. The second is the concatenating assignment operator ('.='), which appends the argument on the right side to the argument on the left side.

Example -

<?php $a = '12345'; // This works: echo "qwe{$a}rty"; // qwe12345rty, using braces echo "qwe" . $a . "rty"; // qwe12345rty, concatenation used // Does not work: echo 'qwe{$a}rty'; // qwe{$a}rty, single quotes are not parsed echo "qwe$arty"; // qwe, because $a became $arty, which is undefined ?>

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Array operators

The + operator returns the right-hand array appended to the left-hand array; for keys that exist in both arrays, the elements from the left-hand array will be used, and the matching elements from the right-hand array will be ignored.

Example -

<?php $a = array("a" => "apple", "b" => "banana"); $b = array("a" => "pear", "b" => "strawberry", "c" => "cherry"); $c = $a + $b; // Union of $a and $b echo "Union of \$a and \$b: \n"; var_dump($c); $c = $b + $a; // Union of $b and $a echo "Union of \$b and \$a: \n"; var_dump($c); $a += $b; // Union of $a += $b is $a and $b echo "Union of \$a += \$b: \n"; var_dump($a); ?>

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Operator Precedence

The precedence of an operator specifies how "tightly" it binds two expressions together. For example, in the expression 1 + 5 * 3, the answer is 16 and not 18 because the multiplication ("*") operator has a higher precedence than the addition ("+") operator. Parentheses may be used to force precedence, if necessary. For instance: (1 + 5) * 3 evaluates to 18. When operators have equal precedence their associativity decides how the operators are grouped. For example "-" is left-associative, so 1 - 2 - 3 is grouped as (1 - 2) - 3 and evaluates to -4. "=" on the other hand is right-associative, so $a = $b = $c is grouped as $a = ($b = $c).

Operators of equal precedence that are non-associative cannot be used next to each other, for example 1 < 2 > 1 is illegal in PHP. The expression 1 <= 1 == 1 on the other hand is legal, because the == operator has lesser precedence than the <= operator. Use of parentheses, even when not strictly necessary, can often increase readability of the code by making grouping explicit rather than relying on the implicit operator precedence and associativity.

Example -

<?php $x = 4; // this line might result in unexpected output: echo "x minus one equals " . $x-1 . ", or so I hope\n"; // because it is evaluated like this line: echo (("x minus one equals " . $x) - 1) . ", or so I hope\n"; // the desired precendence can be enforced by using parentheses: echo "x minus one equals " . ($x-1) . ", or so I hope\n"; ?>

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Bitwise Operators

Bitwise operators allow evaluation and manipulation of specific bits within an integer.Bit shifting in PHP is arithmetic. Bits shifted off either end are discarded. Left shifts have zeros shifted in on the right while the sign bit is shifted out on the left, meaning the sign of an operand is not preserved. Right shifts have copies of the sign bit shifted in on the left, meaning the sign of an operand is preserved.

If both operands for the &, | and ^ operators are strings, then the operation will be performed on the ASCII values of the characters that make up the strings and the result will be a string.

Example -

<?php /* * Ignore the top section, * it is just formatting to make output clearer. */ $format = '(%1$2d = %1$04b) = (%2$2d = %2$04b)' . ' %3$s (%4$2d = %4$04b)' . "\n"; echo <<<EOH --------- --------- -- --------- result value op test --------- --------- -- --------- EOH; /* * Here are the examples. */ $values = array(0, 1, 2, 4, 8); $test = 1 + 4; echo "\n Bitwise AND \n"; foreach ($values as $value) { $result = $value & $test; printf($format, $result, $value, '&', $test); } echo "\n Bitwise Inclusive OR \n"; foreach ($values as $value) { $result = $value | $test; printf($format, $result, $value, '|', $test); } echo "\n Bitwise Exclusive OR (XOR) \n"; foreach ($values as $value) { $result = $value ^ $test; printf($format, $result, $value, '^', $test); } ?>

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