Functions In PHP

• A block of code for specific tasks.
• Save compile time –only compile once.
• Reuse many times when needed.
• Optimize your code.

Built-in functions like print(); date();

• User-defined functions:
• Function names cannot have spaces.
• Function name must begin with letter or underscore.

E.g., call a built-in function abs();

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<?php $num=-5; $new_num=abs($num); echo $new_num; ?>

Declaring a Function

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function function_name(arguments) { block of codes and statements; }

• You can declare a function below a call to it.
• May have none, one, or multiple arguments each separated by a comma.
• Write function name followed by ( ), even if the function doesn’t have any arguments.

Example-

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<?php function print_br($str) { print "$str <br>"; } print_br("line1"); print_br("line2"); ?>

Functions – Return Value

• Functions may have a return value.
• A return value in a function, returns the value to the function that may be used later on while calling a function.
• You may need to access the value that the function returns, but you may not need to print it out, that’s why you use a return value for a function.

Example-Functions – Return Value

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<?php function multiply_by_two($value){ $result=$value*2; return $result; } echo multiply_by_two(7); ?>

Example-Functions – Without Return Value

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<?php function multiply_by_two($value){ $result=$value*2; echo $result; } multiply_by_two(7); ?>

PHP built-in Functions
Sqrt(); — Take the square root of a number
Ceil(); — Take ceil of a decimal number
Floor(); — take the floor of a decimal number
Max(); — take the max number
Min(); — take the min number
Strtolower(); — convert string to lower case
Strtoupper(); — convert string to upper case