Is there an xml_encode() like json_encode() in PHP?

Question

In PHP it is easy to pass back an json objects by using the json_encode().
However is there an XML equivalent of this?

Answer 1

here is one for php7.0+ , i bet it is far from optimal , the code is non-trivial, and it has NOT been tested much, but at least it works for my data (unlike Seph's code)...

example:

$test = array (
        'normal1' => 'foo',
        'normal2' => 'bar',
        'foo_assoc' => [ 
                'foo',
                'bar',
                'baz',
                [ 
                        'derp',
                        'derpmore' 
                ] 
        ],
        'foo_nonassoc' => [ 
                'derppp' => 'yes',
                'daarpp' => 'no',
                'lel',
                'far' => 'away' 
        ],
        'normal3' => 'lala',
        'deep' => [ 
                'deeper' => [ 
                        'deeper2' => [ 
                                'deepest' => [ 
                                        'quite',
                                        'deep',
                                        'indeed' 
                                ],
                                'checkmate' 
                        ] 
                ] 
        ],
        'special' => 'encodingcharacters&test',
        'me_n_you' => 'true' 
);

echo (hhb_xml_encode ( $test ));

output:

foo
bar
foo
bar
baz
derp
derpmore

  yes
  no
  lel
  away

lala

  
    
      quite
      deep
      indeed
      checkmate
    
  

encoding<special>characters&test
true

function:

• Edit: fixed a bug with encoding empty arrays.
• Edit: made the code PHP8-compatible

    function hhb_xml_encode(array $arr, string $name_for_numeric_keys = 'val'): string {
        if (empty ( $arr )) {
            // avoid having a special case for  and  i guess
            return '';
        }
        $is_iterable_compat = function ($v): bool {
            // php 7.0 compat for php7.1+'s is_itrable
            return is_array ( $v ) || ($v instanceof \Traversable);
        };
        $isAssoc = function (array $arr): bool {
            // thanks to Mark Amery for this
            if (array () === $arr)
                return false;
            return array_keys ( $arr ) !== range ( 0, count ( $arr ) - 1 );
        };
        $endsWith = function (string $haystack, string $needle): bool {
            // thanks to MrHus
            $length = strlen ( $needle );
            if ($length == 0) {
                return true;
            }
            return (substr ( $haystack, - $length ) === $needle);
        };
        $formatXML = function (string $xml) use ($endsWith): string {
            // there seems to be a bug with formatOutput on DOMDocuments that have used importNode with $deep=true
            // on PHP 7.0.15...
            $domd = new DOMDocument ( '1.0', 'UTF-8' );
            $domd->preserveWhiteSpace = false;
            $domd->formatOutput = true;
            $domd->loadXML ( '' . $xml . '' );
            $ret = trim ( $domd->saveXML ( $domd->getElementsByTagName ( "root" )->item ( 0 ) ) );
            assert ( 0 === strpos ( $ret, '' ) );
            assert ( $endsWith ( $ret, '' ) );
            $full = trim ( substr ( $ret, strlen ( '' ), - strlen ( '' ) ) );
            $ret = '';
            // ... seems each line except the first line starts with 2 ugly spaces,
            // presumably its the  element that starts with no spaces at all.
            foreach ( explode ( "\n", $full ) as $line ) {
                if (substr ( $line, 0, 2 ) === '  ') {
                    $ret .= substr ( $line, 2 ) . "\n";
                } else {
                    $ret .= $line . "\n";
                }
            }
            $ret = trim ( $ret );
            return $ret;
        };
        
        // $arr = new RecursiveArrayIterator ( $arr );
        // $iterator = new RecursiveIteratorIterator ( $arr, RecursiveIteratorIterator::SELF_FIRST );
        $iterator = $arr;
        $domd = new DOMDocument ();
        $root = $domd->createElement ( 'root' );
        foreach ( $iterator as $key => $val ) {
            // var_dump ( $key, $val );
            $ele = $domd->createElement ( is_int ( $key ) ? $name_for_numeric_keys : $key );
            if (! empty ( $val ) || $val === '0') {
                if ($is_iterable_compat ( $val )) {
                    $asoc = $isAssoc ( $val );
                    $tmp = hhb_xml_encode ( $val, is_int ( $key ) ? $name_for_numeric_keys : $key );
                    // var_dump ( $tmp );
                    // die ();
                    $tmp = new DOMDocument();
                    @$tmp->loadXML ( '' . $tmp . '' );
                    foreach ( $tmp->getElementsByTagName ( "root" )->item ( 0 )->childNodes ?? [ ] as $tmp2 ) {
                        $tmp3 = $domd->importNode ( $tmp2, true );
                        if ($asoc) {
                            $ele->appendChild ( $tmp3 );
                        } else {
                            $root->appendChild ( $tmp3 );
                        }
                    }
                    unset ( $tmp, $tmp2, $tmp3 );
                    if (! $asoc) {
                        // echo 'REMOVING';die();
                        // $ele->parentNode->removeChild($ele);
                        continue;
                    }
                } else {
                    $ele->textContent = $val;
                }
            }
            $root->appendChild ( $ele );
        }
        $domd->preserveWhiteSpace = false;
        $domd->formatOutput = true;
        $ret = trim ( $domd->saveXML ( $root ) );
        assert ( 0 === strpos ( $ret, '' ) );
        assert ( $endsWith ( $ret, '' ) );
        $ret = trim ( substr ( $ret, strlen ( '' ), - strlen ( '' ) ) );
        // seems to be a bug with formatOutput on DOMDocuments that have used importNode with $deep=true..
        $ret = $formatXML ( $ret );
        return $ret;
    }