$re = '/createElement\(\s*\'(.*)\'\,\s*/';
$str = 'return createElement(
\'div\',
{ className: \'sidebar-options\' },
createElement(
\'div\',
{ className: \'account-options\' },
createElement(
\'div\',
null,
\'My Account\'
),
createElement(
\'div\',
null,
\'Sign Out\'
)
),
createElement(TextField, { props: foo }, \'blah\'),
createElement(
\'div\',
{ className: \'room-options\' },
createElement(
\'div\',
null,
\'Change Duration\'
),
createElement(
\'div\',
null,
\'Make Private\'
),
createElement(
\'div\',
null,
\'Delete Conversation\'
)
)
);';
$subst = "R.$1(";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php