$re = '/^\s+,?\[([A-Za-z0-9]+)\]\s=\s([A-Za-z0-9\@]+),?/m';
$str = ' [UserLoginName] = @UserLoginName,
,[UserExternalId] = @UserExternalId
,[UserName] = @UserName
,[Password] = @Password
,[IsWindowsUser] = @IsWindowsUser
,[Active] = @IsActive
,[MustChangePassword] = @MustChangePassword
,[PasswordExp] = @PasswordExp
,[PasswordModifiedDate] = @PasswordModifiedDate
,[PasswordPolicyName] = @PasswordPolicyName
,[LoginTry] = @LoginTry
,[PermissionsRefreshDate] = @PermissionsRefreshDate
,[FirstName] = @FirstName
,[LastName] = @LastName
,[EmailAddress] = @EmailAddress
,[DefaultStoreId] = @DefaultStoreId
,[EmployeeNumber] = @EmployeeNumber
,[Phone] = @Phone
,[MobilePhone] = @MobilePhone
,[Address1] = @Address1
,[Address2] = @Address2
,[PostalCode] = @PostalCode
,[PostalAddress] = @PostalAddress
,[Title] = @Title
,[Language] = @Language
,[BirthDate] = @BirthDate
,[EmploymentDate] = @EmploymentDate
,[ResignationDate] = @ResignationDate
,[BankaccountNo] = @BankaccountNo
,[SocialSecurityNo] = @SocialSecurityNo
,[Comment] = @Comment
,[Country] = @Country
,[vudGUID] = @VudGUID
,[CreatedByUserId] = @CreatedByUserId
,[ModifiedByUserId] = @ModifiedByUserId
,[CreatedDate] = @CreatedDate
,[ModifiedDate] = @ModifiedDate
,[UseSingleSignOn] = @UseSingleSignOn
,[Salt] = @Salt
,[IsSystemUser] = @IsSystemUser';
$subst = "[\1] = ISNULL(\2, [\1]),";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php