<?php

use Doctrine\Common\Lexer\AbstractLexer;

class MathLexer extends AbstractLexer
{
    /**
     * better: a token for every operator
     * instead of T_OPERATOR
     */
    const T_OPERATOR = 1;
    
    const T_FORMULA = 2;
    
     /**
     * Lexical catchable patterns.
     *
     * @return array
     */
    protected function getCatchablePatterns()
    {
        return array(
            '[\+\-\/\*]+',
            '[a-zA-Z]+',
        );
    }

    /**
     * Lexical non-catchable patterns.
     *
     * @return array
     */
    protected function getNonCatchablePatterns()
    {
        return array(
            '\s+',
        );
    }

    /**
     * Retrieve token type.
     *
     * @param string $value
     *
     * @return integer
     */
    protected function getType(&$value)
    {
        if (preg_match('/[\+\-\/\*]+/', $value)) {
            return self::T_OPERATOR;
        }
        
        return self::T_FORMULA;
    }
}

$lexer = new MathLexer();
$lexer->setInput('X + Y - Z');

$lexer->moveNext();
while(null !== $lexer->lookahead) {
    // lookahead is an array with token elements
    // value: value of token
    // position: position in initial string
    // type: integer (see constants)
    echo '"' . $lexer->lookahead['value'] . '"';
    echo ' is of type ' . $lexer->lookahead['type'] . PHP_EOL;
    $lexer->moveNext();
}

"X" is of type 2
"+" is of type 1
"Y" is of type 2
"-" is of type 1
"Z" is of type 2

• get a partial reference in Doctrine
• Caching Doctrine results for performance
• Read class metadata of your Doctrine entities

PHP 8.3, Laminas MVC 3.2, Symfony 5.2, Laravel 8.28, PHPUnit 9.5, Doctrine ORM 2.8