Dakusan’s Domain > Archive > Posts > 2016

Date: 07/02/16 06:51am

Painless migration from PHP MySQL to MySQLi

The PHP MySQL extension is being deprecated in favor of the MySQLi extension in PHP 5.5, and removed as of PHP 7.0. MySQLi was first referenced in PHP v5.0.0 beta 4 on 2004-02-12, with the first stable release in PHP 5.0.0 on 2004-07-13^[1]. Before that, the PHP MySQL extension was by far the most popular way of interacting with MySQL on PHP, and still was for a very long time after. This website was opened only 2 years after the first stable release!

With the deprecation, problems from some websites I help host have popped up, many of these sites being very, very old. I needed a quick and dirty solution to monkey-patch these websites to use MySQLi without rewriting all their code. The obvious answer is to overwrite the functions with wrappers for MySQLi. The generally known way of doing this is with the Advanced PHP Debugger (APD). However, using this extension has a lot of requirements that are not appropriate for a production web server. Fortunately, another extension I recently learned of offers the renaming functionality; runkit. It was a super simple install for me.

From the command line, run “pecl install runkit”
Add “extension=runkit.so” and “runkit.internal_override=On” to the php.ini

Besides the ability to override these functions with wrappers, I also needed a way to make sure this file was always loaded before all other PHP files. The simple solution for that is adding “auto_prepend_file=/PATH/TO/FILE” to the “.user.ini” in the user’s root web directory.

The code for this script is as follows. It only contains a limited set of the MySQL functions, including some very esoteric ones that the web site used. This is not a foolproof script, but it gets the job done.

//Override the MySQL functions
foreach(Array(
    'connect', 'error', 'fetch_array', 'fetch_row', 'insert_id', 'num_fields', 'num_rows',
    'query', 'select_db', 'field_len', 'field_name', 'field_type', 'list_dbs', 'list_fields',
    'list_tables', 'tablename'
) as $FuncName)
    runkit_function_redefine("mysql_$FuncName", '',
        'return call_user_func_array("mysql_'.$FuncName.'_OVERRIDE", func_get_args());');

//If a connection is not explicitely passed to a mysql_ function, use the last created connection
global $SQLLink; //The remembered SQL Link
function GetConn($PassedConn)
{
    if(isset($PassedConn))
        return $PassedConn;
    global $SQLLink;
    return $SQLLink;
}

//Override functions
function mysql_connect_OVERRIDE($Host, $Username, $Password) {
    global $SQLLink;
    return $SQLLink=mysqli_connect($Host, $Username, $Password);
}
function mysql_error_OVERRIDE($SQLConn=NULL) {
    return mysqli_error(GetConn($SQLConn));
}
function mysql_fetch_array_OVERRIDE($Result, $ResultType=MYSQL_BOTH) {
    return mysqli_fetch_array($Result, $ResultType);
}
function mysql_fetch_row_OVERRIDE($Result) {
    return mysqli_fetch_row($Result);
}
function mysql_insert_id_OVERRIDE($SQLConn=NULL) {
    return mysqli_insert_id(GetConn($SQLConn));
}
function mysql_num_fields_OVERRIDE($Result) {
    return mysqli_num_fields($Result);
}
function mysql_num_rows_OVERRIDE($Result) {
    return mysqli_num_rows($Result);
}
function mysql_query_OVERRIDE($Query, $SQLConn=NULL) {
    return mysqli_query(GetConn($SQLConn), $Query);
}
function mysql_select_db_OVERRIDE($DBName, $SQLConn=NULL) {
    return mysqli_select_db(GetConn($SQLConn), $DBName);
}
function mysql_field_len_OVERRIDE($Result, $Offset) {
    $Fields=$Result->fetch_fields();
    return $Fields[$Offset]->length;
}
function mysql_field_name_OVERRIDE($Result, $Offset) {
    $Fields=$Result->fetch_fields();
    return $Fields[$Offset]->name;
}
function mysql_field_type_OVERRIDE($Result, $Offset) {
    $Fields=$Result->fetch_fields();
    return $Fields[$Offset]->type;
}
function mysql_list_dbs_OVERRIDE($SQLConn=NULL) {
    $Result=mysql_query('SHOW DATABASES', GetConn($SQLConn));
    $Tables=Array();
    while($Row=mysqli_fetch_assoc($Result))
        $Tables[]=$Row['Database'];
    return $Tables;
}
function mysql_list_fields_OVERRIDE($DBName, $TableName, $SQLConn=NULL) {
    $SQLConn=GetConn($SQLConn);
    $CurDB=mysql_fetch_array(mysql_query('SELECT Database()', $SQLConn));
    $CurDB=$CurDB[0];
    mysql_select_db($DBName, $SQLConn);
    $Result=mysql_query("SHOW COLUMNS FROM $TableName", $SQLConn);
    mysql_select_db($CurDB, $SQLConn);
    if(!$Result) {
        print 'Could not run query: '.mysql_error($SQLConn);
        return Array();
    }
    $Fields=Array();
    while($Row=mysqli_fetch_assoc($Result))
        $Fields[]=$Row['Field'];
    return $Fields;
}
function mysql_list_tables_OVERRIDE($DBName, $SQLConn=NULL) {
    $SQLConn=GetConn($SQLConn);
    $CurDB=mysql_fetch_array(mysql_query('SELECT Database()', $SQLConn));
    $CurDB=$CurDB[0];
    mysql_select_db($DBName, $SQLConn);
    $Result=mysql_query("SHOW TABLES", $SQLConn);
    mysql_select_db($CurDB, $SQLConn);
    if(!$Result) {
        print 'Could not run query: '.mysql_error($SQLConn);
        return Array();
    }
    $Tables=Array();
    while($Row=mysql_fetch_row($Result))
        $Tables[]=$Row[0];
    return $Tables;
}
function mysql_tablename_OVERRIDE($Result) {
    $Fields=$Result->fetch_fields();
    return $Fields[0]->table;
}

And here is some test code to confirm functionality:

global $MyConn, $TEST_Table;
$TEST_Server='localhost';
$TEST_UserName='...';
$TEST_Password='...';
$TEST_DB='...';
$TEST_Table='...';
function GetResult() {
    global $MyConn, $TEST_Table;
    return mysql_query('SELECT * FROM '.$TEST_Table.' LIMIT 1', $MyConn);
}
var_dump($MyConn=mysql_connect($TEST_Server, $TEST_UserName, $TEST_Password));
//Set $MyConn to NULL here if you want to test global $SQLLink functionality
var_dump(mysql_select_db($TEST_DB, $MyConn));
var_dump(mysql_query('SELECT * FROM INVALIDTABLE LIMIT 1', $MyConn));
var_dump(mysql_error($MyConn));
var_dump($Result=GetResult());
var_dump(mysql_fetch_array($Result));
$Result=GetResult(); var_dump(mysql_fetch_row($Result));
$Result=GetResult(); var_dump(mysql_num_fields($Result));
var_dump(mysql_num_rows($Result));
var_dump(mysql_field_len($Result, 0));
var_dump(mysql_field_name($Result, 0));
var_dump(mysql_field_type($Result, 0));
var_dump(mysql_tablename($Result));
var_dump(mysql_list_dbs($MyConn));
var_dump(mysql_list_fields($TEST_DB, $TEST_Table, $MyConn));
var_dump(mysql_list_tables($TEST_DB, $MyConn));
mysql_query('CREATE TEMPORARY TABLE mysqltest (i int auto_increment, primary key (i))', $MyConn);
mysql_query('INSERT INTO mysqltest VALUES ()', $MyConn);
mysql_query('INSERT INTO mysqltest VALUES ()', $MyConn);
var_dump(mysql_insert_id($MyConn));
mysql_query('DROP TEMPORARY TABLE mysqltest', $MyConn);

Date: 07/02/16 05:54am

Bullet Help Formatter for Python’s argparse

This is a HelpFormatter for Python’s argparse class which:

Takes raw input and wraps long lines to indent against the current line start.
When an indented/list line is encountered, which starts with spaces followed by a star "*", wrapped line’s indents will start 2 spaces after the star.
Lines attempt to split at words of 10 characters or less (see .MinCharsInSplitWord).
If a line needs to split along a word longer than this, a hyphen is inserted at the end of the line.

import argparse
import re
class BulletHelpFormatter(argparse.HelpFormatter):
    def __init__(self, *args, **kwargs):
        super(BulletHelpFormatter, self).__init__(*args, **kwargs)
        self.MinCharsInSplitWord=10

    def _split_lines(self, text, width):
        #Split lines around line breaks and then modify each line
        Lines=[]
        for Line in text.splitlines():
            #Get the number of spaces to put at subsequent lines
            #0 if not a list item, oherwise, 2+list item start
            ListEl=re.match(r'^ *\*', Line)
            NumBeginningSpace=(0 if ListEl==None else ListEl.end()+1)

            #Add extra spaces at the beginning of each line to match the start of the current line, and go to a maxium of $width
            IsFirstPass=True
            SpacesToAdd=''
            NumSpacesToAdd=0
            while(True):
                #Get the word break points before and after where the line would end
                MaxLineLen=max(min(width-NumSpacesToAdd, len(Line)), 1)
                PrevWordBreak=CurWordBreak=0
                for WordBreak in re.finditer(r'(?<=\W).|\W|$', Line):
                    PrevWordBreak=CurWordBreak
                    CurWordBreak=WordBreak.start()
                    if CurWordBreak>=MaxLineLen:
                        if CurWordBreak==MaxLineLen:
                            PrevWordBreak=CurWordBreak
                        break

                #If previous wordbreak is more than MinCharsInSplitWord away from MaxLineLen, then split at the end of the line
                IsSplit=(PrevWordBreak<1 or CurWordBreak-PrevWordBreak>self.MinCharsInSplitWord)
                SplitPos=(MaxLineLen if IsSplit else PrevWordBreak)

                #Append the new line to the list of lines
                Lines.append(SpacesToAdd+Line[0:SplitPos]+('-' if IsSplit else ''))
                Line=Line[SplitPos:]

                #If this is the end, nothing left to do
                if len(Line)==0:
                    break

                #If this is the first pass, update line creation variables
                if IsFirstPass:
                    IsFirstPass=False
                    NumSpacesToAdd=NumBeginningSpace
                    SpacesToAdd=(' ' * NumSpacesToAdd)

        return Lines