Re: MySQL resource

> $result = mysql_query($query, $this->connection); > > if ($result) { > echo (mysql_num_rows($result)); > } > > The way I read the manual, the if() only fires off if the query is > executed, and then by definition mysql_num_rows() should contain at > least a 0. So why do I get this error? > > Warning: Supplied argument is not a valid MySQL result resource in > C:\blah\class_test.inc on line 195 > > If I echo($result) it comes back as > > 1 The result of the query function is a "resource" NOT a boolean. This situation is confusing because the prototype, ie the letter of the law, in the manual (http://www.php.net/manual/en/function.mysql-query.php) says "resource" but the explanatory text then goes on to talk about TRUE and FALSE. You will find this elsewhere in PHP where the casual approach to data-typing allows use/abuse of what some have been trained to see as 'rules'! In fact if you drop in various echo/prints to monitor the process: (warning: I've hacked out this code from within an existing application and flattened out the function calls - so it may not run if you cut-and-paste, as-is) $WhereClause = 'Where phase=1 Order by search'; $tablename = "tblPList_tst"; if (DEBUG) echo " tbl=$tablename~"; $query = "select * from $tablename ".$WhereClause; if (DEBUG) echo "<br>Fn MySQLdbRead: Query=".$query; $queryresourceresult = mysql_query($query, $dbLinkId); if (DEBUG) echo "~Result=".$queryresourceresult; $num_rows_read = mysql_num_rows($queryresourceresult); if (DEBUG) echo "~ Num rows read=$num_rows_read"; In the browser you will see... 2001-10-12 10:46:06 Executing mainline B.php FnConnectToDatabase~ Fn MySQLdbOpen: LinkIdentifier =Resource id #1 Whereas Select db result =1 FnFetchFirst~ tbl=tblPList_tst~ Fn MySQLdbRead: Query=select * from tblPList_tst Where phase=1 Order by search~Result=Resource id #2~Num rows read=1~ Thus the problematic code (as above) if ($result) { would, in this stub/example, become if ("Resource id #2") { I must admit, most of the time I do NOT bother to check the query result (of a Select). [greater minds might point out some shock-horror that I have casually ignored] Instead I look at the Num-Rows function (in the case of a MySQL Select command) because I am happy to accept a zero-or-more records found response. Of course, if the query is being constructed dynamically, and particularly from some user/foreign input, then this is much too casual even if the code previously implements 'solid' filtering and error-checking precautions! In such as case, more attention is required - as might be appropriate during first stage prototyping in any case. During first-run debugging I might look to see if the QueryResourceResult is false, because that would indicate a syntactically invalid query (tip: most of the time I have checked that by using a command line or MySQL admin tool to prototype the dbquery conversation and when first writing the code I'm copying-and-pasting from there into PHP). In which case one would invert the test and make it thoroughly type-specific: if ( $result === false ) { echo "invalid query - rejected by MySQL"; } Trust this helps, =dn