What does function mean in php

function is a custom function

For example:

function jia（$a） {
$b = $a+10;
return $b;
}

The above is a custom function, see below See how to use it (recommended learning: PHP video tutorial)

echo jia（‘10’）；

The displayed result is 20 //Here jia is the custom function name, so just give $a any number The returned results are all 10. This is a customized function. This example is very simple~ But by customizing the function, you will find that everything becomes better.

A function can be defined by the following syntax:

Pseudocode showing the purpose of the function

<?php
function foo($arg_1, $arg_2, /* ..., */ $arg_n)
{
    echo "Example function.\n";
    return $retval;
}
?>

Any valid PHP code has May appear inside a function, even in other function and class definitions.

The function name has the same naming rules as other identifiers in PHP. Valid function names begin with a letter or underscore, followed by letters, numbers, or underscores. It can be expressed as a regular expression: [a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*.

Note: When a function is conditionally defined, it must be defined before calling the function.

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