仅当没有具有相同值的键时才添加到数组？

I want to add $variable only if there isn't a key with the same value in array $insertar["Atributos"].

$insertar["Atributos"][] = $variable;

I can do it using a foreach to check beforehand if $variable is stored and insert only if it isn't but I want to know if there is an easier way.

To be clear:

I want to add $variable only if there isn't a key with the same value in array $insertar["Atributos"].

# check if $variable exists as a value in $insertar["Atributos"], and not a key
if (in_array($variable, $insertar["Atributos"])) {
    # add $variable as a VALUE to the array
    $insertar["Atributos"][] = $variable;
}

Sorry I read the question wrong. Try if (! in_array($value, $array)) { ... }

At first I thought you meant if the value is a key. If you want to check if a key is in an array use isset($array[$key]) rather than array_key_exists because isset will perform much faster on long arrays.

Alternative cleanup and post-processing approach:

$insertar = array_map("array_unique", $insertar);

See array_unique(). Implicitly orders the value entries however.

Use a simple construct like this:

if(! in_array($variable, $insertar["Atributos"])){
    array_push($variable,$insertar["Atributos"]);
}