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Asked: 2026-05-11T18:17:45+00:00

I use SQL_CALC_FOUND_ROWS in Mysql SELECT statement, to get the number of lines my

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I use SQL_CALC_FOUND_ROWS in Mysql SELECT statement, to get the number of lines my SELECT would return without a LIMIT clause.

$sql = new mysqli('localhost', 'root', '');
$sql->select_db('mysql');
$s1 = $sql->query('select SQL_CALC_FOUND_ROWS * from db limit 0, 3');
$s2 = $sql->query('select FOUND_ROWS()');
if($row = $s2->fetch_row()) printf('%d/%d', $s1->num_rows, $row[0]);

On my WinXP dev station it return 3/0 everytime for several weeks. When I use another MySQL server from my station it return 3/0 too.
On anothers PC the same code runs fine, and return the correct number (3/17 for example, if I have 17 records in mysql.db table). Every XP PC have the same PHP/Mysql version, and it ran fine in the past on my PC
Using Mysql Query Browser with the same SQL queries I get the right number.

Could anyone give me an idea of solution, without re-install all?

Sorry, my previous request was awfully unclear.

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1 Answer

  1. Editorial Team

    Thank you.

    When I ran something analogous to your example on the mysql command line, it would work; but running it from php, it failed. The second query has to “know about” the first one, so I figure somehow that persistence/memory linking the two queries was getting messed up by the php.

    (It turns out that WordPress uses this type of query to do its pagination – so our larger problem was that the pagination in a wordpress install suddenly stopped working when we moved to php 5.2.6 … eventually tracked it down to the FOUND_ROWS()).

    Just for the sake of posting for people who may run into this in the future… for me it was the php setting “mysql.trace_mode” – this defaulted “on” in 5.2.6 instead of “off” like previously, and for some reason prevents the FOUND_ROWS() from working.

    As a “fix”, we could either put this in every php page (actually, in a common “include”):

    ini_set("mysql.trace_mode", "0");

    or add this to the .htaccess:

    php_value mysql.trace_mode "0"

    Thanks again,
    Jerry

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