PHP 5.6.0 released

is_string

(PHP 4, PHP 5)

is_stringComprueba si una variable es de tipo string

Descripción

bool is_string ( mixed $var )

Obtiene si la variable dada es de tipo string.

Parámetros

var

La variable a ser evaluada.

Valores devueltos

Devuelve TRUE si var es de tipo string, FALSE de lo contrario.

Ejemplos

Ejemplo #1 Ejemplo is_string()

<?php
$values 
= array(falsetruenull'abc''23'23'23.5'23.5''' ''0'0);
foreach (
$values as $value) {
    echo 
"is_string(";
    
var_export($value);
    echo 
") = ";
    echo 
var_dump(is_string($value));
}
?>

El resultado del ejemplo sería:

is_string(false) = bool(false)
is_string(true) = bool(false)
is_string(NULL) = bool(false)
is_string('abc') = bool(true)
is_string('23') = bool(true)
is_string(23) = bool(false)
is_string('23.5') = bool(true)
is_string(23.5) = bool(false)
is_string('') = bool(true)
is_string(' ') = bool(true)
is_string('0') = bool(true)
is_string(0) = bool(false)

Ver también

  • is_float() - Comprueba si el tipo de una variable es float
  • is_int() - Comprueba si el tipo de una variable es integer
  • is_bool() - Comprueba si una variable es de tipo booleano
  • is_object() - Comprueba si una variable es un objeto
  • is_array() - Comprueba si una variable es un array

add a note add a note

User Contributed Notes 3 notes

up
2
laszlo dot heredy shift-two gmail etc
6 months ago
Using is_string() on an object will always return false (even with __toString()).

<?php
class B {
  public function
__toString() {
    return
"Instances of B() can be treated as a strings!\n";
  }


$b = new B();
print(
$b); //Instances of B() can be treated as a strings!
print(is_string($b) ? 'true' : 'false'); //false
?>
up
-7
slicky at newshelix dot com
13 years ago
Be aware that this function could result into unwanted results if you check single chars in an array.
For instance:
You have a simple string and want to repeat this string evertime it ends.

<?php
for ($i=0; $i < strlen($string);$i++){
    if(!
is_string($key[$x]))
       
$x = 0;
    echo
$key[$x];
   
$x++;
}
?>

This will print you out the key, but won't iterate it since $x won't be reset. is_string function will give out true at element in that string, even if it doesn't exist. for instance is_string $key[1000] while your string is just 10chars long.
However this doesn't matter just use $key[$x] == '' instead.
Of course you won't use this to iterate a string, but you might come across something where this get useful, for instance for a en/decrypt engine.
up
-20
Sammy Moshe
1 year ago
The cool thing about this function is that it lets you be a lot more specific with your logic than you could have been before. And since I'm all about explicit control, when it comes to code, this one gets me all hot and bothered.

<?php
    
//Like this. You could also do the reverse of it.
    
if(is_string($variable) ) && !is_array($variable) ){
         
//Do something that appeals to your controlling nature.
    
}

?>

God bless those php dev guys for thinking of everything.
To Top