[PHP] Convert a date from french month name to another format

convert_date_fr.php

<?php
/**
 * Convert a date from french month name to another format
 * 
 * @param string  Date to convert
 * @param string  Format of date to convert
 * @param string  Format for output
 * @return string  
 * 
 * @php_version  >= 5.3
 * @link http://php.net/manual/en/function.date.php  All date formats
 */
function convert_date_fr($date, $format_in = 'j F Y', $format_out = 'Y-m-d') {
    // French to english month names
    $months = array(
        'janvier' => 'january',
        'février' => 'february',
        'mars' => 'march',
        'avril' => 'april',
        'mai' => 'may',
        'juin' => 'june',
        'juillet' => 'july',
        'août' => 'august',
        'septembre' => 'september',
        'octobre' => 'october',
        'novembre' => 'november',
        'décembre' => 'december',
    );
    
    // List of available formats for date
    $formats_list = array('d','D','j','l','N','S','w','z','S','W','M','F','m','M','n','t','A','L','o','Y','y','H','a','A','B','g','G','h','H','i','s','u','v','F','e','I','O','P','T','Z','D','c','r','U');
    
    // We get separators between elements in $date, based on $format_in
    $split = str_split($format_in);
    $separators = array();
    $_continue = false;
    foreach($split as $k => $s) {
        if($_continue) {
            $_continue = false;
            continue;
        }
        // For escaped chars (like "\h")
        if($s == '\\' && isset($split[$k+1])) {
            $separators[] = '\\' . $split[$k+1];
            $_continue = true;
            continue;
        }
        if(!in_array($s, $formats_list)) {
            $separators[] = $s;
        }
    }
    
    // Translate month name
    $tmp = preg_split('/('.implode('|', array_map(function($v) {
        if($v == '/') {
            return '\/';
        }
        return str_replace('\\', '\\\\', $v);
    }, $separators)).')/', $date);
    
    foreach($tmp as $k => $v) {
        $v = mb_strtolower($v, 'UTF-8');
        if(isset($months[$v])) {
            $tmp[$k] = $months[$v];
        }
    }
    
    // Re-construct the date
    $imploded = '';
    foreach($tmp as $k => $v) {
        $imploded .= $v . (isset($separators[$k]) ? str_replace('\\', '', $separators[$k]) : '');
    }
    
    return DateTime::createFromFormat($format_in, $imploded)->format($format_out);
}

tests.php

<?php

echo convert_date_fr('5 février 2018'); // => 2018-02-05
echo convert_date_fr('8 Décembre', 'j F', 'd/m'); // => 08/12
echo convert_date_fr('8-août 2018 14:30:54', 'j-F Y H:i:s', 'Y-m-d H:i:s'); // => 2018-08-08 14:30:54
echo convert_date_fr('8 août \à 14\h30', 'j-F \à H\hi', 'Y-m-d H:i:s'); // => 2018-08-08 14:30:00
echo convert_date_fr('8 Février \à 14\h30', 'j-F \à H\hi', 'd/m \à H\hi'); // => 08/02 à 14h30
echo convert_date_fr('18/12/2018', 'd/m/Y', 'Y-m-d'); // => 2018-12-18
echo convert_date_fr('18/12/2018', 'd/m/Y', 'j F Y'); // => 18 December 2018
echo convert_date_fr('8 Février à 14h30', 'j-F \à H\hi', 'd/m \à H\hi'); // => fail