isset
serialize
Funções para Manipulação de variáveis
PHP Manual

# print_r

(PHP 4, PHP 5)

print_r — Prints human-readable information about a variable

### Descrição

mixed print_r ( mixed `$expression` [, bool `$return` = false ] )

print_r() displays information about a variable in a way that's readable by humans.

print_r(), var_dump() and var_export() will also show protected and private properties of objects with PHP 5. Static class members will not be shown.

Remember that print_r() will move the array pointer to the end. Use reset() to bring it back to beginning.

### Parâmetros

`expression`

  The expression to be printed.

`return`

  If you would like to capture the output of print_r(), use the `return` parameter. When this parameter is set to `TRUE`, print_r() will return the information rather than print it.

### Valor Retornado

If given a string , integer or float , the value itself will be printed. If given an array , values will be presented in a format that shows keys and elements. Similar notation is used for object s.

When the `return` parameter is `TRUE`, this function will return a string . Otherwise, the return value is `TRUE`.

### Notas

> Nota: Esta função usa o interno buffer de saída com este parâmetro, então assim não pode ser usado dentro de uma função de callback para ob_start().

### Histórico

Versão | Descrição
--- | ---
4.3.0 | The `return` parameter was added. If you need to capture the output of print_r() with an older version of PHP prior, use the output-control functions.
4.0.4 | Prior to PHP 4.0.4, print_r() will continue forever if given an array or object that contains a direct or indirect reference to itself. An example is print_r($GLOBALS) because $GLOBALS is itself a global variable that contains a reference to itself.

### Exemplos

Exemplo #1 print_r() example

`<pre>
<?php
$a = array ('a' => 'apple', 'b' => 'banana', 'c' => array ('x', 'y', 'z'));
print_r ($a);
?>
</pre>`

O exemplo acima irá imprimir:

    <pre>
    Array
    (
        [a] => apple
        [b] => banana
        [c] => Array
            (
                [0] => x
                [1] => y
                [2] => z
            )
    )
    </pre>

Exemplo #2 `return` parameter example

`<?php
$b = array ('m' => 'monkey', 'foo' => 'bar', 'x' => array ('x', 'y', 'z'));
$results = print_r($b, true); // $results now contains output from print_r
?>`

### Veja Também

- ob_start() - Ativa o buffer de saída
- var_dump() - Mostra informações sobre a variável
- var_export() - Mostra ou retorna uma representação estruturada de uma variável

isset
serialize
Funções para Manipulação de variáveis
PHP Manual