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 yaz_scan    (PHP 4 >= 4.0.5, PECL) yaz_scan -- Prepares for a scan 说明void  yaz_scan ( resource id, string type, string startterm [, array flags] ) 
   This function prepares for a Z39.50 Scan Request on the specified 
   connection.
   
   To actually transfer the Scan Request to the server and receive the
   Scan Response, yaz_wait() must be called. Upon
   completion of yaz_wait() call
   yaz_error() and yaz_scan_result() to
   handle the response.
   参数
    - id
 
       The connection resource returned by yaz_connect().
       - type
 
       Currently only type rpn is supported.
       - startterm
 
       Starting term point for the scan.
       
       The form in which the starting term is specified is given by parameter
       type.
       
       The syntax this parameter is similar to the RPN query as described in
       yaz_search(). It consists of zero or more 
       @attr-operator specifications, then followed by 
       exactly one token.
       - flags
 
       This optional parameter specifies additional information to control 
       the behaviour of the scan request. Three indexes are currently read 
       from the flags array:
       number (number of terms requested),
       position (preferred position of term) and
       stepSize (preferred step size).
       
  
  例
    例子 1. PHP function that scans titles 
<?php function scan_titles($id, $startterm)  {   yaz_scan($id, "rpn", "@attr 1=4 " . $startterm);   yaz_wait();   $errno = yaz_errno($id);   if ($errno == 0) {     $ar = yaz_scan_result($id, &$options);     echo 'Scan ok; ';     while (list($key, $val) = each($options)) {       echo "$key = $val  ";     }     echo '<br /><table>';     while (list($key, list($k, $term, $tcount)) = each($ar)) {       if (empty($k)) continue;       echo "<tr><td>$term</td><td>$tcount</td></tr>";     }     echo '</table>';   } else {     echo "Scan failed. Error: " . yaz_error($id) . "<br />";   } } ?>
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