<?php
$reg = "/^[A-Z]{2,3}[\d]{3}$/";
$string1 = "USA097 WO : SWAP DE GABINETE";
$string2 = "WO : SWAP DE AV222 GABINETE";
$array1 = explode(" ", $string1);
$array2 = explode(" ", $string2);
 
foreach($array1 as $cadena){
    if(preg_match($reg, $cadena)){
        $objetivo = $cadena;
        break;
    }
}
echo strlen($objetivo) ? $objetivo : "No se encontró la cadena";
 
echo "\r\n";
 
foreach($array2 as $cadena){
    if(preg_match($reg, $cadena)){
        $objetivo = $cadena;
        break;
    }
}
echo strlen($objetivo) ? $objetivo : "No se encontró la cadena";

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