my own language

A module to evaluate expressions typed by the user in another GUI. In other words I need the ability to have my own script language. Some of the features are: - evaluate complex expression like this var_1 = ( var_2 + var_3 ) / my_function( var4, my_second_function ( "constant" ) ) ; - the user can create his own functions function my_new_function ( par1, par2 ) { a = 1; b = 2; return a + b; } - support matrix variables - basic programming structures IF, WHILE, FOREACH, FOR, EXIT, RETURN if ( boolean_var ) { for i = 0 to length( var_matrix ) { print "value of position " + i + " : " + var_matrix[ i ]; } } else { print "nothing"; } ## Deliverables 1) Complete and fully-functional working CLASS(s) in complete source code of all work done. 2) Deliverables must be in ready-to-run condition, ## Platform php 4.3 +