Spiff this up a bit:

* output data returned by the eval; prints strings and numbers directly, var_dump()s arrays and objects
* if no returned data, print a line break. This makes things easier when doing 'echo' and you forget to add one yourself.
* Add some documentation comments

diff --git a/maintenance/eval.php b/maintenance/eval.php
index c53da36..9ef4958 100755 (executable)
--- a/maintenance/eval.php
+++ b/maintenance/eval.php
@@ -1,6 +1,17 @@
 <?php
 /**
- * @todo document
+ * PHP lacks an interactive mode, but this can be very helpful when debugging.
+ * This script lets a command-line user start up the wiki engine and then poke
+ * about by issuing PHP commands directly.
+ *
+ * Unlike eg Python, you need to use a 'return' statement explicitly for the
+ * interactive shell to print out the value of the expression. Multiple lines
+ * are evaluated separately, so blocks need to be input without a line break.
+ * Fatal errors such as use of undeclared functions can kill the shell.
+ *
+ * To get decent line editing behavior, you should compile PHP with support 
+ * for GNU readline (pass --with-readline to configure).
+ *
  * @package MediaWiki
  * @subpackage Maintenance
  */
@@ -10,13 +21,17 @@ require_once( "commandLine.inc" );
 
 do {
        $line = readconsole( "> " );
-       eval( $line . ";" );
+       $val = eval( $line . ";" );
+       if( is_null( $val ) ) {
+               echo "\n";
+       } elseif( is_string( $val ) || is_numeric( $val ) ) {
+               echo "$val\n";
+       } else {
+               var_dump( $val );
+       }
        if ( function_exists( "readline_add_history" ) ) {
                readline_add_history( $line );
        }
 } while ( 1 );
 
-
-
-
 ?>