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v5:reference:connection:param [2020/01/25 00:33] – [Usage] Improve code layout, add comment for param reset dregadv5:reference:connection:param [2021/02/26 01:35] (current) – Call with falsy values: param(false) vs param(0) - see #682 dregad
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 This method is used with [[v5:userguide:learn_bind:bind_vars|bind variable SQL statement execution]], to produce injection resistant code. This method is used with [[v5:userguide:learn_bind:bind_vars|bind variable SQL statement execution]], to produce injection resistant code.
  
-On RDBMS with positional (numbered) query parameters such as PostgreSQL, calling ''param(false)'' will reset the parameter counter, allowing to start building a new query.+On RDBMS with positional (numbered) query parameters such as PostgreSQL, calling ''param()'' with a "falsy" value((equivalent to ''false''; read the //Converting to boolean// section in the [[https://www.php.net/manual/en/language.types.boolean.php|PHP manual]])) will reset the parameter counter, allowing to start building a new query without first executing the previous one. 
 + 
 +<WRAP tip> 
 +Note that calling ''param(false)'' **only** resets the counter, //without returning a placeholder//. This allows forcing a reset operation independently from building a query; the next invocation will return the first placeholder. 
 + 
 +Compare that with ''param(0)'' or ''param(%%''%%)'', which both resets **and** returns the first placeholder. 
 + 
 +This is illustrated in the examples below. 
 +</WRAP> 
 + 
  
 ------------------------------ ------------------------------
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 <code php> <code php>
 $sql1 = 'SELECT * FROM accounts WHERE '  $sql1 = 'SELECT * FROM accounts WHERE ' 
-    . 'name  = ' . $db->param('account') . ' AND '+    . 'name = '  . $db->param('account') . ' AND '
     . 'total = ' . $db->param('amount');     . 'total = ' . $db->param('amount');
  
-$db->param(false); // Reset param count+// Reset param count as a standalone operation then build the query 
 +$db->param(false);
 $sql2 = 'SELECT * FROM accounts WHERE id = ' . $db->param('id'); $sql2 = 'SELECT * FROM accounts WHERE id = ' . $db->param('id');
 +
 +// Reset param count with a "falsy" value while building the query
 +$sql3 = 'SELECT * FROM accounts WHERE '
 +    . 'name = ' . $db->param(0) . ' AND '
 +    . 'status = ' . $db->param(1);
 </code> </code>
 +
 +
  
 See below for the code's output with various database drivers. See below for the code's output with various database drivers.
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 $sql1: SELECT * FROM accounts WHERE name = ? AND total = ? $sql1: SELECT * FROM accounts WHERE name = ? AND total = ?
 $sql2: SELECT * FROM accounts WHERE id = ? $sql2: SELECT * FROM accounts WHERE id = ?
 +$sql3: SELECT * FROM accounts WHERE name = ? AND status = ?
 </code> </code>
  
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 <code> <code>
 $sql1: SELECT * FROM accounts WHERE name = :account AND total = :amount $sql1: SELECT * FROM accounts WHERE name = :account AND total = :amount
-$sql2: SELECT * FROM accounts WHERE id = :id"+$sql2: SELECT * FROM accounts WHERE id = :id 
 +$sql3: SELECT * FROM accounts WHERE name = :0 AND status = :1
 </code> </code>
  
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 $sql1: SELECT * FROM accounts WHERE name = $1 AND total = $2 $sql1: SELECT * FROM accounts WHERE name = $1 AND total = $2
 $sql2: SELECT * FROM accounts WHERE id = $1 $sql2: SELECT * FROM accounts WHERE id = $1
 +$sql3: SELECT * FROM accounts WHERE name = $1 AND status = $2
 </code> </code>
 +
 +Without the parameter reset, //$sql2// would be ''... id = $3'' and //$sql3// ''... name = $4 AND status = $5'', which would result in errors when calling [[v5:reference:connection:execute|]].
  
v5/reference/connection/param.1579908788.txt.gz · Last modified: 2020/01/25 00:33 by dregad