Variable Parsing in PHP

Introduction

In this article I will explain Variable Parsing in PHP. When a string is in double quotes or in heredoc, the variables are parsed within it. It can be explained with two simple examples and a complex example and the complex syntax can be recognized by the curly braces. The simple one is most common and convenient, it is provides a way to variable.

Example 1

If a dollar sign ($) is encountered then the parser will take as many tokens as possible to form a valid variable name. Such as:

<?php

$name = "MCN";

echo "Company name is the $name solution.".PHP_EOL ." ";

//invalid. 's' is a valid character for a variable name, but the variable is $name.

echo "Company name is the $names.";

Output

Example 2

<?php

$c_name = array("MCN", "TCS", "company" => "Acencher");

echo "Company name is the $c_name[0] .".PHP_EOL ." ";

echo "Company name is the $c_name[1] .".PHP_EOL ." ";

echo "Company name is the $c_name[0] .".PHP_EOL ." ";

echo "Company name is the $c_name[company] .".PHP_EOL ." ";

class people

{

public $manish = "manish sharma";

public $nitin = "nitin bhardwaj";

public $sharad = "sharad gupata";

public $rahul = "rahul sharma";

}

$emp = new people();

echo "$emp->manish works in $c_name[0] company.".PHP_EOL." ";

echo "$emp->nitin works in $c_name[1] company.".PHP_EOL." ";

echo "$emp->sharad works in $emp->nitin company.".PHP_EOL." ";

echo "$emp->nitin said hello to $emp->manish.".PHP_EOL." ";

Output

Example 3

Complex (Curly) Syntax

This is not called complex because the syntax is complex, it is called complex because it allows the use of complex expressions. This example show all errors.

<?php

// Show all errors

error_reporting(E_ALL);

$invititation = 'hello sir!'." ";

echo "This is {$invititation}"." ";

echo "This is ${$invititation}"." ";

echo "This square is {$square->width}00 centimeters broad."." ";

echo "This works: {$arr['key']}"." ";

echo "This works: {$arr[4][3]}"." ";

echo "This is wrong: {$arr[name][3]}"." ";

echo "This works: {$arr['name'][3]}"." ";

echo "This works: " . $arr['name'][3]." ";

echo "This works too: {$obj->values[3]->name}"." ";

echo "This is the value of the var named $name: {${$name}}"." ";

echo "This is the value of the var named by the return value of getName(): {${getName()}}"." ";

echo "This is the value of the var named by the return value of \$object->getName(): {${$object->getName()}}"." ";

echo "This is the return value of getName(): {getName()}"." ";

It's also possible to access class properties using variables within strings like using this syntax.

<?php

class name

{

var $man = 'I am man.';

}

$name = new name();

$man = 'man';

$sharas = array('Nitin', 'man', 'sharas', 'rahul');

echo "{$name->$man}"." ";

echo "{$name->$sharas[1]}";

Output