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I used this statement to determine whether a

these values and converts them into arrays before calling the updateRec()func- tion. It s much easier to work with the fields and values as arrays than in thesomewhat amorphous context they embody after smartRToEdit()or rToEdit(). function updateRec($tableName, $fields, $vals){ //expects name of a record, fields array values array//updates database with new valuesglobal $dbConn; $output = ?; $keyName = $fields[0]; $keyVal = $vals[0]; $query = ?; $query .= UPDATE $tableName SET \n ?; for ($i = 1; $i < count($fields); $i++){ $query .= $fields[$i]; $query .= = ; $query .= $vals[$i]; $query .= ,\n ?; } // end for loop//remove last comma from output$query = substr($query, 0, strlen($query) - 2); $query .= \nWHERE $keyName = $keyVal ?; $result = mysql_query($query, $dbConn); if ($result){ $query = SELECT * FROM $tableName WHERE $keyName = $keyVal ?; $output .=

update successful

\n ?; $output .= new value of record:
?; $output .= qToTable($query); } else { $output .=

there was a problem…

$query

\n ?; } // end ifreturn $output; } // end updateRec421Chapter
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I used this statement to determine whether a

I used this statement to determine whether a field is a foreign key: } else if (preg_match( /(.*)ID$/ ?, $col, $match)) { It uses a simple but powerful regular expression: /(.*)ID$/. This expressionlooks for any line that ends with ID. (Recall that the $indicates the end of astring.) The .*indicates any number of characters. The parentheses around .*tellPHP to store all the characters before IDinto a special array, called $match. Since there s only one pattern to match in this expression, all the characters before IDcontain the table name. So, this regular expression takes thename of a field and determines if it ends with ID. If so, the beginning part of the field name (everything but ID) is stored to $match[1]. If $colcontainsoperationID, this line returns TRUE(becauseoperationIDends with ID) andthe table name (operation) is stored in $match[1]. Building the Foreign Key List BoxIf a field is a foreign key reference, it is necessary to build a list box containingsome sort of meaningful value the user can read. Since I need this capability ina couple of places (and smartRToEdit()is already pretty complex), I build a newfunction called fieldToList(). This function (explained in detail later in the Building a List Box from a Field ? section of this chapter) builds a drop-downHTML list based on a table and field name. Rather than worrying about thedetails of the fieldToList()function here, I simply figured out what parametersit would need and printed that function s results. Working with Regular FieldsAny field that is not a primary or foreign key is handled by the elseclause, whichprints out an rToEdit()-style textbox for user input. This textbox handles allfields that allow ordinary user input, but will not trap for certain errors (such asstring data being placed in numeric fields or data longer than the underlyingfield accepts). These would be good code improvement. If the data designer didnot name foreign key references according to my convention, those fields are stilleditable with a textbox, but the errors that could happen with rToEdit()areworth concern. Committing a Record UpdateThe end result of either rToEdit()or smartRToEdit()is an HTML form containinga table name and a bunch of field names and values. The updateRecord.phptakesTRICK420PHP5/MySQLProgrammingfortheAbsoluteBeginner
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HERE; return $output; } // end smartRToEditWhat makes

function allows the user to type any index number into the textbox with- out any real indication what data correlates to that index. This versionbuilds a drop-down list showing operation names. The key value associatedwith those names is stored in the value attribute of each option. (Detailsto follow in the fieldToList()function.) The user doesn t have to knowanything about foreign key references or relational structures he simplychooses an operation from a list. That list is dynamically generated eachtime the user chooses to add a record, so it always reflects all the opera- tions in the agency. Neither a primary nor secondary key.In this case, I print a simple textboxso the user can input the value of the field. In all cases, the output willreflect the current value of the field. Working with the Primary KeyThe primary key value is much more important to the program than it is to theuser. I decided to display it, but not to make it editable in any way. Primary keysshould not be edited, but changed only by adding or deleting records. I relied upon some conventions to determine whether a field is a primary key. Iassumed that the first field of the record (field number 0) is the primary key. Thisis a very common convention, but not universal. Since I created the data design inthis case, I can be sure that the number 0 field in every table is the primary key. For that field, I simply printed the field name and value in an ordinary HTML tablerow. I added the key s value in a hidden field so the next program has access to it. Recognizing Foreign KeysUnfortunately, there is no way (at least in MySQL or SQLite) to determine if a fieldis a foreign key reference. I had to rely on a naming convention to make sure myprogram recognizes a field as a foreign key reference. I decided that all foreignkey fields in my database will have the foreign table s name followed by the valueID. For example, a foreign key reference to the operationtable will always becalled operationIDin my database. This is a smart convention to follow anyway, as it makes your field names easy toremember. It becomes critical in smartRToEdit()because it s the only way to tellwhether a field is a foreign key reference. I used an else ifclause to check thename of any field that is not the primary key (which was checked in the ifclause). The preg_match()function lets me use a powerful regular expressionmatch to determine the field s name.
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HERE; return $output; } // end smartRToEditWhat makes

HERE; return $output; } // end smartRToEditWhat makes this function smart is its ability to examine each field in the recordand make a guess about what sort of field it is. Figure 12.13 shows the result ofthe smartRToEdit()program so you can compare it to the not-so-clever functionin Figure 12.12. Determining the Field TypeAs far as this function is concerned, three field types in a record need to be han- dled differently. Primary key.If a field is the primary key, its value needs to be passed on tothe next program, but the user should not be able to edit it. Foreign key.If a field is a foreign key reference to another table, the usershould only be able to indirectly edit the value. The best approach is tohave a drop-down list box that shows values the user will recognize. Eachof these values corresponds to a key in that secondary record. For example, in Figure 12.13 there is a list box for the operationIDfield. The operationIDfield is a foreign key reference in the agenttable. The ordinary rToEdit() 418PHP5/MySQLProgrammingfortheAbsoluteBeginnerFIGURE 12.13The smarterfunction preventsthe user fromediting the primarykey and provides adrop-down list forall foreign keyreferences.
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