Functions
- Always use descriptive function names.
- PHP doesn’t support function overloading!
- Functions are case-insensitive (but its good practice to use the declared name when invoking).
- All PHP functions and classes have global scope. They can be called from outside the function even if they were defined inside and vice versa. Have a look at the code below to understand this!
function test(){
echo 'test';
function testInner(){
echo 'test inner';
}
}
test(); // if you don't call it before calling testInner(), you will get an error.
testInner();- You can pass arguments by value, or by reference, or default argument values.
- Variable arguments:
function sum(...$args) {
echo gettype( $args ); // array!
// you can loop through array items using 'foreach'
foreach ($args as $arg) {
// process argument here.
}
}
sum( 1, 3, 4 );
sum(1, , 4, 5, 23, 5 );
// in older version of php, you can do above like:
function sum(){
foreach (func_get_args() as $arg) {
// process arg here.
}
}
sum( 1, 3, 4 );
sum(1, , 4, 5, 23, 5 );- It is possible to declare the type of argument, a function receives. And once declared, if you don’t supply exact type, you will get an error.
function test( int $a, string $b ){
var_dump( $a );
var_dump( $b );
}
test( 1, 'name' ); // no error
test( null, 1 ); // fetal error- function_exists(): checks whether a function exists or not.
- get_defined_functions(): returns an array of defined functions.
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